I saw Slayer at Ozzfest \'99. Not really into that kind of thing now, but I was then.
Trouble is, it was at Shoreline Ampitheatre in Mountain View, California (just south of San Francisco.) Basically the seats are near the stage...then the grass, IE the pit, is about three miles back. So um yeah it was kinda crazy...at this point in the middle / front (of the grass...miles away from the stage). but so long as you avoided that you were fine. I think the distance probably tamed it some...I imagine it\'s hard to mosh properly when the performers appear to be the size of small insects. Also the grass itself is pretty wide, so it\'s easy to avoid that center area.
Hm that probably doesn\'t really help...all I can say is have fun and try not to get hurt.