Is it a confirmed suite upgrade? I've stayed here a lot and have never seen the inside of a suite, so if its space-available, you might not actually get one. I think they may have a relatively limited #.
The rooms are beautiful (modern Hyatt with Thai touches) so I assume the suites are as well.
Still, its one of my favorite hotels, period.
The staff is wonderful, the Grand Club is exquisite imho, and the location is primo. Ask for a room facing the racecourse.