Ah, Details
A few days ago I’d written about the fix for VMs rebooting after being VMotioned. In the comments there was some speculation about what the big problem would be for ESX 3.5 Update 3. That question was just answered: “Virtual Machines may unexpectedly reboot after a VMotion migration to an ESX 3.5 Update 3 Host OR after a Power On operation on an ESX 3.5 Update 3 Host, when the VMware HA feature with Virtual Machine Monitoring is active.” KB 1007899 has the information you want. I nominate VMware ESX for inclusion in the software defect hall of fame, alongside Mediawiki and Sendmail.