Stayed here recently for a night. Was deciding between another night at the Hyatt Union Square or trying 48 Lex for the first time. I happened to be in the area and showed up in person to ask what rooms would be available for a complimentary Diamond upgrade (wouldn't usually do this, but I didn't want to pay for the slightly more expensive 48 Lex and be stuck in the room type booked when I knew Union Square could at least give me a somewhat better room). Was told a Premier King on a fairly high floor was available, so I booked the standard Studio King and checked in.
The room was actually not very big (can't imagine it was more than 350 square feet), and there was a stain (it was more than discoloration--there was also a change of texture; in a post 9/11 world, I could see someone thinking it was a suspicious white power) in the carpet (which was also fraying quite severely where it met the tile). I called guest services and asked about being moved. I got a call back from housekeeping saying the stain was permanent as they had just cleaned the carpets, so I went downstairs to the front desk to ask for a room change. I spoke with someone at the front desk who was not the initial check-in clerk with whom I had discussed upgrades. I asked for a room change and was told that only standard rooms were available, at which point I asked if he could just refund my room and I'd move down to Union Square. He ended up "seeing what he could do" and was able to move me to a somewhat (but not significantly) larger room with a terrace on a lower floor. I was fine with that room, so didn't complain. Not sure, though, why I didn't just get that room anyway as a Diamond (and I was checking in somewhat late at 7pm)?
Breakfast was also not compliant with Diamond benefits, which provides one entrée, juice, and coffee, inclusive of tax and gratuity. Breakfast at this property was limited to $25 per person. The cheapest entrée ($14) plus juice ($5) and coffee ($8) before tax and tip appeared to be $27 ($29.40 with tax). Also, the thin slices of toast that came with my eggs may have been the worst bread/toast I've had since staying in a hostel in Cambodia.
Didn't really notice any problems with street noise even on the 4th floor.
As mentioned, in my review of the Union Square property (
http://www.flyertalk.com/forum/22092964-post51.html), definitely prefer the Andaz 5th Ave despite the greater street noise or the Grand Hyatt. 48 Lex was slightly more disappointing than Union Square, and I would probably take Union Square over 48 Lex for its better location and more modern design (48 Lex looks much more like a boring business hotel).