Below you'll find some of the experiences I made, while I was on vacation in La Reunion in June 2003. It is only a short and very rough review of this oversea department of France and all prices are as of June 2003.

La Reunion is located in the Indian Ocean just 1 hour flight to the east of Madagaskar. Alhtough 11000 km seperated from the mainland, the island is an oversea department of France. Correspondingly, the official language is french and the currency is the Euro.
La Reunion is a rather small island of about 60 km in diameter, however, distances between single locations can get quite large due to the rugged terrain of the island. Only a belt of about 5 km size around the island exist with a more or less flat landscape along the costal lines. This is also the zone where most of the 700.000 inhabitants of La Reunion live. Since every family on the island owns at least one car (totalling in about 200.000 cars) and just one through-road exists, the consequence is a tremendous traffic chaos at almost any time of the day. Traffic jams are not an exception but rather the rule. At one day it took us 2 hours to drive 30 km! Especially at the weekends, beaches and popular vacation spots are absolutely overcrowded around the island. However, the more you come into the interior of La Reunion, the less people you'll see. Especially the Cirque de Mafate is a true hiking paradise. Also, places which can only be reached by longer trails tend to be less crowded. For all other popular spots, the rule is to start early in the morning and leave again by noon.
The weather on La Reunion is moderate throughout the year. There are only small differences between summer and winter. However, the local weather drastically depends on the location. The west side of the island is the sunny side, it almost never rains there since the mountains block the clouds which move in from the east. Accordingly the east side is very wet. It rains there at least once a day, sometimes even the complete day. It is very humid and warm and therefore the preferred region to grow fruits and vegetables. Along the coastline it is very warm and sunny but the further you come into the interior of La Reunion the colder it gets. Especially in the cirques the nights can get quite cold. Also, vegetation changes very drastically with elevation. You can almost see any type of vegetation on the island.
A view words to language issues: since french is the official and only language of the island, it's certainly not a bad idea to know at least some basic french words and phrases. We've made the experience that almost none of the inhabitants of La Reunion speak english. This is also true for guest houses and expecially important for hikes in the cirques and accomodations in the mountain huts. There are some exceptions but they are rather rare. The general rule is: the younger the person the higher the probability that he/she can speak at least some english.

Best time to go to La Reunion is between April and November. This is the winter season and temperatures are a little more moderate than in the summer. More importantly, the weather is more dry and cyclones are not an issue. Keep in mind that July and August are the most favorite vacation months for people coming from the french mainland. At this time of the year many hotels are fully booked and popular tourist spots become more crowded. From my point of view, best time is May or June.
Considering the length of your stay...it depends a little bit on your interests. If you only want to see the mountain region around the cirques and the volcano in a nutshell without serious hiking, 7-10 days should do it. However, for an in-depth overview of the island, 2-3 weeks are the minimum. Especially the hikes in the cirques are very time consuming not to speak of drives around the island. Please note that the beaches of La Reunion are not considered to be first class beaches. They are absolutely not suitable for swimming since either the surf is too high to even consider swimming or the water is very shallow (about 0.5 - 1 m deep) with large boulders, coralles and sea urchins at the ground. Good for snorkeling but bad for swimming. Therefore, my recommendation is to spend a little more than 2 weeks on La Reunion, doing serious hiking and then fly to Mauritius (about 30 min. flight) and relax another 5 days at first class beaches. If you still have time, there are enough hidden places on La Reunion like small waterfalls and bassins, however, I would account a complete day to explore each of those destinations.

Main entry point to La Reunion is St. Denis in the north. Most people come to La Reunion by plane, although a ferry from Mauritius to La Reunion exists. Main connection between France and La Reunion is a direct flight from Paris Orly to St. Denis. It takes about 11 hours and the cheapest option is an overnight flight. You can also try to catch cheaper flights to Mauritius of Madagaskar first and then fly to St. Denis but usually the final price is about the same. Please note that you have to change airports in Paris if you come from any other country than France itself. Due to this fact, the average travel time from any city in europe to St. Denis is about 24 hours including all stop-overs (this is, of course, using the most affordable fare). The only company which flies directly from Paris to St. Denis is Air France. Accordingly, prices are rather high and especially during the peak season in July / August, places fill up quickly.

By bus and train:

As far as I know there is no train connection on La Reunion, however, the bus system is quite good and very affordable. You can reach almost any destination on the island by bus if you bring enough time. There are 12 major routes around the island and into the cirques and many smaller lines between single locations. All busses go on a regular basis, usually several times a day. Fares are surprisingly low. An example: a one way trip from St. Denis into Cirque de Salazie (Hell Bourg) is about 6 Euro per person. For travelers with a limited budget the bus system might be a good option.

By car:

Certainly the most flexible way to get to know La Reunion. However, as I said before, the complete island is a single traffic jam, especially during peak times (morning and afternoon). So it is by far not relaxing to drive on the island. Also, driving times can get quite large. An example: driving from St. Pierre in the south to St. Benoit in the north on road N3 takes you about 3 hours (not considering traffic jams), although the distance is only 50 km. This is due to the uncountable number of ups and downs and bends on the road. There is rarely a straight piece of road which is longer than 200 m on the complete island.
Gas prices are slightly higher than in europe but no big issue. Driving times might be high but the distances are on a rather small scale. Also, you don't want to rent a big car since parking space around the island is limited and the roads in the mountains tend to get really narrow in places.
Speaking of rental cars: there are many rental companies around the island. Most of them are located in St. Denis, the larger ones at the airport. All major companies like Hertz, Avis and so on have their counter at the international airport but also a few smaller ones like Au-Bas-Prix. Rates are affordable and range in between 200 and 300 Euro per week including insurance for a small Peugeot 206.

There are several types of accomodation on La Reunion. First, the typical european standard hotel with typical european prices. Such resorts are mainly found on the sunny west side of the island close to the beaches. A more affordable way to spend the night is to book the so called Chambre d'hotes, guest houses offering rooms with breakfast. They usually have a good standard and you get a double room with shower for about 50 Euro per night. You have to pay extra for dinner though, which is another 15 Euro per person. You can also rent appartments on the island. They are usually well equipped so you can prepare your own food. Prices range in between 30 and 60 Euro per night per appartment for 2-6 person. I haven't seen any campsite on La Reunion and I've also hearded that it is not recommended to camp at beaches due to the high crime rate on the island. Most travel guides also don't recommend camping.
Standard accomodation for longer hikes on La Reunion are the mountain huts, called Gites de la Montagne. Their quality varies drastically from location to location, however, prices are more or less the same, about 15 Euro per person per night plus additional 15 Euro per person for dinner. Don't expect to have any comfort, the huts are only equipped with the absolute basics like bed, linen and water. Some have double rooms but many have general sleeping rooms fitting up to 15 person.
Maybe a few words to the typical dinner on La Reunion, especially in the mountain huts. The standard meal is called Carri and is a combination of rice, sausages (sometimes beef or chicken) and a bean sauce. You won't find any other option in the mountain huts, only small variation exist. You also won't find a menu to choose from, either you eat Carri or you go to bed very hungry (unless you bring your own food). From my point of view it is ok to eat Carri for 2 or 3 days in a row, however, for longer trips I would defenitely bring my own food at least for some days. Also, the typical breakfast on La Reunion (like in mainland France) is really very very small. Usually just a few pieces of white bread, butter and a single type of jelly. But don't count on it...sometimes you don't even get white bread but small cookies. For guys like me who are used (and need) a good breakfast in the morning, this is a nightmare! So please keep that in mind when you consider to stay in a mountain hut.

Every smaller village has either a supermarket or a small epicerie with good selections. However, prices are about 10-20 % higher than in France. Look for local food like fish or fruits. Often, there are small stands at the roadside offering fruits for a reasonable price, sometimes cheaper than in the supermarkets and always fresh. The larger supermarkets in the bigger towns have all the selections you also find in continental europe.

I hope, that helped a little bit for those of you who are planning on going to La Reunion. If you have questions, email me.