I'm staying at the hotel, so I go to the gym quite often anyway. One of the instructors told me they just opened up for members, and that they're running promotions. Part of it is that if you join now, you won't pay till July.
I like their equipment, and there's always staff around to help you out with your training program. They're also going to start aerobics lessons. But I haven't seen any other gym in Doha, so not quite sure how they compare.