vSphere GA?

You know it will not take long when KB articles start popping up:

vSphere Client overview performance charts might not appear for ESX hosts prior to ESX 4.0 (1010568)        KB Article
vSphere environment that contains hosts running ESX 3.x earlier, some of the overview performance charts do not display data after you install or upgrade to vCenter Server 4.0. In such cases, a No data available message…

How to create default alarms when upgrading to vSphere 4.0 (1010399)        KB Article
Some of the default alarms included with vSphere 4.0 are not created on your system when you upgrade from a previous version. SQL scripts that ensure that the default alarms are added to your system are attached…

And there’s plenty more where that came from…. Just do a search on the KB site with the keyword “vSphere”.