Following a blog post from an MS Engineer, Installed Server 2008 standard x64 on my TabletPC adding in many of the vista features. It smokes my install of Vista Ultimate to pieces...
Performance tests have shown a 11-17% performance difference between a Server 2008 WS and Vista, SP1. This is the OS MS should have released to the desktop!
Here's a guide to add more stuff...
I'm working on a scripted install so I'll keep you posted!