My mysql is not used by a forum, so it might be a little offtopic here, but you wanted the OS+mysql combination, so I'm going to post it anyway:
Queries per second avg: 983.444
The OS is a 64-bit Linux, mysql 5.0.20 (I know I should upgrade, but it hasn't been stopped for over a year, I don't have the heart to shut it down

). The machine is a dual-Xeon Intel.
I'm very satisfied with the mysql performance.