Excellent location and great staff!
Stayed here for 3 nights on a getaway. Loved it. Every staff member we encountered was friendly and professional. Our room was on a corner on the 17th floor. It was well laid out with a GREAT bed and a spacious bathroom.
The location can't be beat! We flew in/out of Newark. You can take the airport express bus for something like $26 roundtrip, and it will drop you off 4-5 blocks from the hotel. It may sound like a lot, but Manhattan North-South blocks are small. It's a quick walk from the bus drop off/pick up. The hotel is also only two short blocks from a subway station - and I might be stating the obvious here, but you can get within walking distance of many, many places in Manhattan on the subway. Do yourself a favor and if you're going to be in town for 3+ days and doing a lot of exploring - get an unlimited ride Metrocard. 
Or if you're the walking type, you can get to Times Square, Grand Central, Central Park, Park Ave, 5th Ave, MOMA, The United Nations (I know I'm digressing) all on foot, no subway required.
It's tough to beat the Hyatt 48 for its location and modern feel. My only ding is like others have said - the charging for wifi is egregious. Not only that - if you have more than one device - they'll charge you for all of them!
Would return in a heartbeat.