As a European in the states I always get amazed on how quickly everything happens in restaurants. In the US it feels like you are in and out in about an hour, compared to home where we tend to eat for hours (often because of really slow service). Places I can recommend for dinner in New York are Spice Market (Meatpacking), Monkey Bar (Midtown) and in particular The Standard Grill (Meatpacking). Not really my kind of place but should you feel like mingling with look-a-likes from The Sopranos and The Real Housewives of Manhattan, mixed with a few celebrities like Victoria Beckham, then pay a visit to Cipriani Downtown (SoHo).
Some of the best bars in New York are located in hotels and the age of the crowd often ranges from 20-something to 50-something. An alternative to the roof top bar at The Peninsula is the bar at Hotel Gansevoort in Meatpacking district. In SoHo, the bar at SoHo Grand is also a great place for an after dinner cocktail. The hottest of hot places is supposedly Empire hotel on Upper West side as scenes from SATC 2 are being shot there, as well as the roof top bar Boom Boom Room at The Standard (Meatpacking).