I stayed at this hotel once in 2012 and several times in 2011 (I think four stays total, 3-4 nights each).
The nicest thing about this hotel is that the suites are enormous, probably the largest I've stayed in in Manhattan. I've been told by staff that there is actually no management relationship between this hotel and the Setai in Miami, but it resembles the Miami Setai in that the suite is pretty much an apartment. You have a living room (an actual separate room, not a living "area" like in some hotel suites), tons of closet space, and a real kitchen fully equipped with pots and pans, silverware, blender, etc. You can really cook in this hotel, which is definitely nice if you want to entertain or if you're staying for a long time.
The decor is sophisticated and clean, lots of creams and browns and grays. It's polished but ends up feeling a bit corporate and lacking in soul. A bit corporate and lacking in soul could just as well describe the neighborhood surrounding the hotel. It's in a very dull part of Midtown, though it is quite convenient to transportation hubs like Grand Central and Times Square. Entering and exiting the hotel you'll have to deal with crowds of tourists and office workers. It's not a fun neighborhood to walk around and there's not much of interest immediately nearby.
Service is very good, in my experience. The hotel's restaurant is very good as well, but the food is quite over the top: everything is drenched in butter and cream, it's all very heavy. Definitely eat there once during your stay but I wouldn't imagine it'd be a place you'd want to go night after night. Room service is good but not great.
I could see this hotel being ideal for someone who needs a luxurious, long term stay for business in Manhattan. But if you're visiting the city for a romantic trip or want to stay in an interesting neighborhood, you'd be best suited to staying elsewhere (like I decided I was).