I'll second the Mariott Marquis TS, the lobby (8th floor!) is really nice. The Renaissance TS is also really nice, although I had some issues 7 years ago, it was probably an anomaly.
If you're looking for something more affordable, the Pod hotels at TS and 39th Street are very nice, as long as you're not looking for a view or to lounge around your hotel room with room service. They have nice rooftop bars, though, so you can still enjoy a good view. They are my favorite place when it's just me, no family, and I just need a place to crash for the night in midtown, convenient to Penn Station and Grand Central.