Well, this was a happy coincidence.
I had just done some maintenance and needed to rebuild my search index. I have about 100,000 threads in my forum so it was taking forever.
About halfway through I decided to look for a better way to go about it, hoping there was a script or something. Rebuilding the search index is a real pain for a large vb forum.
I came across this hack and it encouraged me to upgrade to mysql 4 and give it a shot. The upgrade to v4 was a cinch, and the hack installed in a straightforward way. It took about an hour and a half to run the SQL commands.
This is the most involved hack I've installed. I run several of my own private hacks but tend to avoid other people's hacks. This one is a winner.
I have between 500 and 700 people online during the day. My servers are seeing decreased load. Unfortunately I didn't capture any statistics beforehand, but from memory I believe my database load is about 2/3rds of what it was. This is significant in my situation as I'm always running out of hardware and vb doesn't scale well beyond 2 servers.
My forums are at:
http://www.rcgroups.com
(the busy forums are in the "electric" section)
Jim