We stayed at the Westin in Feb 2007 and had some wonderful dinners while in St. Martin:
You can't go wrong in Grand Case........ it's like a Gourmet Ghetto(about 15-20 minute drive from Dawn Beach):
Le Pressior - Beautifully prepared and presented....I think the best on the Island
L'Escapade - wonderful... great service
Calmo's Cafe - lots of fun, much more casual experience with feet in the sand...they have live music on a stage set in the ocean
Didn't have a chance to try the new place called "Spicy" but it's pretty inside.
Spiga was recommended too (Italian and very busy)
Plus...they close the street to traffic on Tues. night at 6 PM and have live music and people selling crafts........lots of great energy and fun.
Marigot (about a 25 minute drive):
The concierge recommended La Vie de Rose but I would skip it....I think it's a tourist trap with average food and service.
We sought out Rosemary's from recommendations here and Anthony Bourdain's NY Times article (no one knew where or what it was...it turns out to be a very casual Lolo along the marina across from the Taxi office) and had a mixed experience.....the food was good but the only staff person working (she waited tables, cooked and cleaned) was overwhelmed with 2 tables and sent 3 others away. We wound up receiving plates that contained nothing that we ordered (she chose to give us a little bit of everything except what we requested) but it was good local food and ony cost $40 including a bottle of wine and tip.
Le Sancier for pastries and lunch
Nearer the hotel in Oyster Bay:
Mr. Busby's during the day (kind of average burgers by the beach) and Daniel's at night -(fish and Italian) casual but pricey for what it was.
Le Planteur (in Oyster Pond on the way to Capt. Olivers) - pretty location perched above the Marina. Wonderful French/Creole food with slow service (preference, it seems, is given to the french customers).
The Pizza/DVD place just down the road on on the French side (towards Oyster Pond) had really good pizza!! It looks like it's in someone's garage. Quite a deal at $10 for a large cheese pizza as opposed to $50 for 2 panini's and a piece of cheesecake from room service for the kids at the hotel.