Vincent Vlieghe published an interesting article about how to setup a semi-automated patching system for VMware ESX Server.
At the same time he leaks the information VMware is preparing better patching capabilities for upcoming ESX Server 3.1 and VirtualCenter 2.1.
Read it here.
From a security point of view it’s worth to remember that blind patching is strongly discouraged in production systems (even with official methods), more than ever if we are talking about a mission critical environment like a virtual one.
When budget allows it, testing new patches on lab environments is always the best solution. This imply a complex and expensive infrastructure replicating the production one, even if virtualization mitigates issues in building it.