Absolutely L'Impero. Michael White is the new chef, and the food is stellar as usual. They have a fantastic wine list with really interesting wines by the glass. I also recommend Insieme also with an out of this world wine list, Fiamma, and A Voce.
Sfoglia , L'Impero (new chef is a winner in my book).
And I wouldn't travel for it but if on UES I have been having some nice meals alfresco at Per Lei. Good fresh pastas and very friendly staff. A good all around Summer spot.
A voce is really terrific and I didn't feel rushed at all. I got wines by the glass and they had a nice selection of Italian wines -- at fairly reasonable prices.
Fiamma in Soho..Piano Due in midtown...(Del Posto for a major splurge)....L'Impero..Insieme...so many places....For a less formal environment try: Peasant in NoLita.....