ESX 3.0.1 and VirtualCenter 2.0.1 can now be downloaded. The release comes with a few things such as support for some newer hardware like the Intel Tulsa processor, full support for some 64-bit operating systems and critical bugfixes. I hope that display (GUI) issues in VirtualCenter have been addressed as well.

Also in the package is improved upgrade support. See the updated guide.

UPDATE: some info about the upgrade process can be found here.