Thanks everyone for all of your feedback. Since we're not using any strange hardware (just regular Opteron/Xeon SCSI servers with LSI MegaRaid cards), and since we never expect commerical support, then I guess that answers that.
Wondering... since I brought up MySQL, and a few people (thanks Henning!) said MySQL in particular has problems, I didn't mention that we're about to ditch MySQL anyway, and complete our conversion to PostgreSQL, so I wonder... Does PostgreSQL have the same problems as MySQL on OpenBSD?