On November 23 VMware released the first updated for its vSphere 4.0 platform. The patch is especially important if the customers are implementing or evaluating VDI because it introduces support for View 4.0, and for Windows Server 2008 R2 and Windows 7 guest OSes.
Update 1 also introduced a Pre-Upgrade Checker Tool to recognize configuration issues and minimize the downtime during the upgrade.
Unfortunately it seems that the patch itself causes downtime and VMware had to re-release it the portion for ESX today:
We’ve released a new version of ESX 4.0 Update 1 that resolves the issue with the ESX 4.0 Update 1 install failing, timing out and resulting in the host entering an usable state.
The new version is called ESX 4.0 Update 1A.
Update: It seems that the Update 1 causes some serious issues to ESXi 4.0 too, at the point that VMware recommends to not install the patch on vCenter.
The Update 1A above doesn’t seem to fix the problem, so customers have to wait at the moment.