Room 4 Dessert was a trendy dessert-and-drinks place in Nolita/Soho. I tried it once. The space was moodily lit and trendy, the music was loud, the dessert was ok -- minimalist, well-executed, but unmemorable (so don't ask me what I had!). The place closed recently so I guess the idea didn't have legs.

A larger place in a more accessible location -- Max Brenner, Chocolate by the Bald Man -- has had a good run just off Union Square, the new food mecca. From the reviews I've read I'm not tempted, though I have walked through breathing deeply. They serve more than dessert, though.