My current lab setup is to test SRM mainly so I have 2 SQL 2008 vms, 2 vcenters, 2 Netapp simulators, 2 HP Lefthand simulators, 2 Active Directory vms, 2 Exchange 2010 vms - all of those are Win2008 (except the storage simulators). The remaining vms are a mixture of Win2008, 2003, and Linux with a couple of XP/Win7 vms for various testing purposes.
6 Dell PE R200s with 8gb ram each - Netgear GB switch.
Please keep in mind, however, I am the sole user in the environment, so resource utilization overall is very small.
My previous setup about 4 months ago was to test View, and the performance was acceptable - more a result of the host hardware than the storage though.