Plan 9 does not work with either of the SCSI controllers in ESX(i) 3.5 or less. Plan 9 does run on IDE drives just fine in ESX(i) 4. Plan 9 panicks if you give it more than 2 CPUs on any of them. If you have any questions about getting Plan 9 to run in ESX(i) 4, let me know; I've done it. But you won't get it running in <4 without moar drivers.
--dho
