I spent some time trying to get VMWare to work reliably within Vista, and failed miserably. Since then I've asked many industry 'professionals' who have all said (without any hesitation) that I shouldn't have wasted my time. VMWare itself appears to run just fine in Vista, Vista just doesn't play nicely with the VMWare images that run within it.
Since then we've ditched Vista and we're planning on developing a build standard that is based on Windows XP Pro.
My plan is to use an XP Pro SP2 host, fully patched and locked down, and then to build whatever 'virtual' machines we need for day to day work (initially XP Pro SP2 with tools installed, and BT2).
I'm expecting to see some degredation in the performance of the various tools (especially Nessus) within VMWare, but as we're mainly going to be working in a lab environment I'm not expecting that we'll take too much of a hit.
If it all becomes too slow/unweildy/unmanageable we will just go back to dual-booting XP Pro SP2 with BT2 (or similar).
Hope that's useful to you