Yes, i'm one of the few, the proud, the Gamers that use a Mac....
i'm very used to sleeping my machine by closing the lid. unfortunately the performance post-sleep is degraded nearly every time it wakes. the solution is a SMC reset (CTRL-OPT-SHIFT + Power), but it seems like an unnecessarily consistent need to reset the SMC.
the symptoms are:
post a fresh SMC reset, gaming with 60FPS
post a sleep cycle, 20 FPS
post a second sleep cycle, 9fps...
MacBook Pro with Retina display, OS X Mountain Lion, 256GB SSD & 8GB RAM