We went twice in one week for dinner only to this restaurant owned in partnership with the Le Duc hotel (I believe). The service is absolutely impeccable: the manageress and staff could not have been more helpful. The food was very good indeed -- it specialises in fish, but also had a good selection of other meat dishes as well, and the portion sizes mroe than generous. It is quite expensive, I would agree, but I would say that the price is very much in keeping with eating out at many restaurants on the island, and in this respect alone, is not overpriced. We spent about £130 (=approx $210 or Euro145) on a three course meal with drinks for two. This seems a lot, but in an hotel just up the beach, we spent about £100 ($160/Euro110) on a three course self service buffet meal, with drinks, and the Cafe des Arts meal was in a completely different league.
As for the negative comments on here about being required to wear long trouser: it is indeed on the beachfront, but I don't think the dress code is unreasonable. It's a smart place and is worth the effort of dressing up a bit.
Overall, I would highly recommend you pay this restaurant a visit during your stay on Praslin.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.