Could be a bit more attentive
After their recent renovation, the lobby is fairly impressive and modern. The room had modern decor and was fairly functional apart from the rather small bathroom (but then it is NYC).
We stayed 5 nights had a room on level 25 so there wasn't any noise issues, though not much of a view. 
Even though in NYC, this is rated a four star hotel, we're use to Grand Hyatt being a 5 star hotel so expectations were aligned accordingly. Whilst service was good, I thought house keeping could've been a bit more attentive and noticed that we were low on bath gel etc and replaced (instead we had to ask). Not a big issue but it's the little things that set hotels in this calibre apart. 
Another downfall was the lack of free wifi even in the lobby. Had to rely on 2G speed internet from T-mobile (prepay card) but reception at the Hyatt wasn't that great.
What we were least impress with was the on-site restaurant. Breakfast wasn't included but we ate there twice anyway. First thing you get seated (which can take a while), they'll ask you if you want coffee and orange juice. Don't be fooled, it's not complimentary, in fact it's $6 each, so having both will cost you $12.
The selection of breakfast (a la carte) was alright but not extensive, for two people we paid on average $60+. Not knowing local prices on the first two days, it wasn't so bad, but once you compare to a "normal" breakfast, it's probably 3 times more expensive.
Tip: Walk next door (connected to the hotel) to the food area at Grand Central, there you'll get a decent breakfast for 2 at around $20+ as well as a few shops.
In terms of location, most places were within walking distance. E.g. 20 mins walk to Port Authority Bus Terminal, 30 mins walk to time square. If you're not into walking, jumping into a taxi to go around midtown is generally around $10 (+ $1 tip).
Warning: DO NOT jump onto those human driven tricycles if you're going far. We went on one to go to Korea Town (32nd St) and ended up paying $65! A taxi ride would have costed $15 max.
Overall, our stay was alright but nothing spectacular. Would only stay again if the price was right.