Recently, VMware released their Update Manager to handle patch management of ESX servers.
For those of you who haven't implemented it, here's a setup of reasonably robust scripts to do the patching via the Deployment console.
Just a quick heads-up in case this affects anyone else besides me.
I have a scripted deployment for Windows 2000 servers. It operates doing a PXE boot in DOS mode, copies the install files from the depot and runs the install.