Grand Hyatt, Mumbai
The Grand Hyatt Mumbai is located in the new financial district Bandra and just about 10 - 15 minutes away from the airport. The rooms are very decent and all the restaurants just fantastic, but of course pricy. Staff is very helpful and they even have a small shopping mall in the complex.
Standard rooms cost around 9000 rupees incl. breakfast (around 200 USD).
Careful: Don't use the hotel room phone for your calls, the price is truly a rip off.
Also a bit annoying is the security check, which is like at the airport. But given the problems they had in Mumbai, I can understand it.

Address:
Off Western Express Highway
Santacruz (East), Mumbai 400 055

URL:
mumbai.grand.hyatt.com