BOOK IT NOW!
Just book it. I went through travel sites for three days trying to find the most inexpensive hotel in the city that didn't look like a dungeon and had a fairly nice sized room (for NY). The Hyatt is perfect.
They have completely renovated the hotel. I was here for the GLAAD awards several years ago and it was nice THEN. But it has been totally revamped.
I landed at 5AM and by the time I got to the hotel on Saturday, I knew it was FAR to early to check-in, but Crystal put me right in a room. That's so rare. And she was extremely professional and accommodating. I was beyond happy and honestly felt, "well, if anything bad happens, at least I have a room."
The room was great. Huge bed. Clean. Comfortable colors. Fantastic soaps and shampoos. I took all of them and I never take the products.
Shower was perfect. Always the right temperature.
Hotel bar is a little pricey if you are not used to NY. But I really enjoyed writing at the end of the bar. 
But YOU CAN NOT beat the location. You are literally on top of Grand Central Station. I took the shuttle from JFK and it stops RIGHT in front of the hotel at Grand Central. Walk across the street. Boom. You're there.
Need a subway? You're on top of it. You don't even go outside. the hotel has it's own entrance.
Need a taxi? You're right outside Lexington and they fly by.
There is a Banana Republic and H&M very close for forgotten wardrobe issues.
Be aware they charge $2 to hold your bag. It's a service. Get over it. 
You're a short walk to Broadway and Times Square.
There is a 24/7 cafe/ market. It's a little pricey, but again, it is the convenience of not leaving the hotel. Salads, chicken, sandwiches, fruit. Coffee.
I had an issue with 10 drunk girls the first night at the hotel. VERY loud. But I called the front desk and they were on it in minutes.
I'm telling you, I've researched NY hotels. If you find a great rate at this hotel, do not hesitate. Regardless, I will book again for my next trip because of the location, the shuttle location, the subway, the staff, the market, and the room.