Restaurant Recco - relaxed, not too trendy, good food
Tides, the teensy fish/seafood "shack" on the LES, has one of the most unusual and interesting ceilings you will find anywhere, and the rest of the decor is stylishly charming. (Photos on website.) The food is delicious, and the exceedingly friendly owner, Stephen, goes out of his way to see that diners have an enjoyable experience.
I haven't been to Urena, but from everything I've heard, Alex Urena's Spanish-inspired cuisine is quite interesting. There had been complaints about the decor, particularly the harsh lighting, but I gather those problems have now been addressed. Menu on menupages.