I have to agree with fists. When school rolls around I average 6 hours of sleep between school, work, my girlfriend, a little afternoon down time, and training. That being said, let me tell you that sleeping almost 10 or 11 hours a day this summer has been AMAZING! When I'm striking or grappling, I have the mental awareness to think ahead, to work what I want to, and I don't make nearly as many stupid mistakes while holding pads, or teaching someone something.
It all seems to come together more smoothly. Also, and no less important, is how fresh and recovered i feel. There have been few times where i just feel "too exhausted" to kick the pads.
My opnion: Bodybuilders think sleep is important for growth and recovery that is provided to you via your body's natural production of such hormones while in a deep sleep cycle. I think sleep is important to fighters (who train harder, and longer) for recovery both mentally and physically. If you're so tired you cant keep your eyes open and jaw shut, somebody's going to put you down.