I was there right after it opened, and it had that "hot new restaurant" vibe and very good food. I was there recently, and it was at least 1/2 empty at 7:30 on a Friday night and both the service and food were much less impressive.
The sardines, if on the menu, are quite good. Be prepared for bones, though. You can either take out the backbone or eat it in the fish - your choice.
First of all, let me apologize for getting the name wrong.
I walked in and noticed someone familiar--the owner of Le Bouchon, and it clicked. I now remember reading somewhere that La Sardine is the sister of one of my old favorites.
It was delicious. The tarte a l'oignon was amazing, but the escargots were left wanting something. I had the duck, he had the rabbit. Both tender, cooked to perfection. We went on Monday night, which is when all bottles of wine are 1/2 off. We were able to get a wine that we would have otherwise overlooked because of its price. The service was great, and they didn't even raise an eyebrow when we spilled wine and the table settings needed to be replaced. We laughed when they brought us the bill, because we had such a delightful meal at a relatively low cost (thanks to that 1/2 priced wine).
I recommend it. I can't compare it to what it has been, but I know I hope to spend many Mondays there in the future.