We had a lunch here a few weeks ago.
We had an 11:30 ADR and were seated right away (the whole meal took about an hour and we were on the DxDP, so we each had appetizers, entrees, and desserts). Overall, I can't complain about the service.
Maybe it was because we were on the DxDP (and had dinners at signature restaurants every night) but the food here didn't wow me. The best part of the meal was the bread (which, FWIW was pretty good). The second best part of the meal (from a food perspective) was the fried shrimp appetizer, which was decent but nothing to write home about. For an entree, I had the Mahi Mahi. It was mediocre (think below-average Red Lobster quality). I had the key lime mousse for dessert. It was disappointing (suffice it to say the meal continually went downhill).
Just to give some perspective, on the same day we had lunch at Coral Reef, we had dinner at Flying Fish. The difference in these two restaurants cannot be overstated (yes, I realize Flying Fish is signature and Coral Reef is not). I can't even begin to describe how much better the snapper at Flying Fish was than the Mahi Mahi at Coral Reef. If I was only going to eat at one seafood restaurant in the Epcot area, Flying Fish would win every day of the week and twice on Sunday. Take it from me, the extra $$$ (or use of extra dining credits) is totally worth it.
Put another way, if I had paid OOP for my meal at Coral Reef, I would have been VERY disappointed (we were on a DxDP upgrade from a free
DDP, which made it far less painful). And I really wanted to like this restaurant.
In defense of Coral Reef, I will say that the tank is pretty cool (especially seeing the sharks, sea turtle, and divers). But for me, the mediocre food more than offset this. Given all of the other choices in Epcot, I will not return (in fact, I'm just the opposite of the OP - want to try LeCellier for lunch on my next visit).