Just noticed that vSphere 4.1 Update 2 was released yesterday. Excerpt from the release notes: Whats New Support for new processors – ESXi 4.1 Update 2 supports AMD Opteron 6200 series (Interlagos) and AMD Opteron 4200 series (Valencia). Support for additional guest operating system – ESX 4.1 Update 2 adds support for Ubuntu 11.10 guest operating system. For a complete list of guest operating systems supported with this release. To read the full release notes click here