Not bad, but it could be lower.
My HD 6750 never breaks 65C when gaming (most demanding games I play are GTA IV, Metro 2033, and Crysis 2).
How's your ventilation in your case?
Did your overclock your GPU?
What's your fan speed?
Its not the best case its one of the small ones and has a bigger motherboard in it, no i haven't overclocked, my Gpu fan Speed is about 8000rpm at 70C thanks