Is having antivirus incorporated in the hypervisor better for security or is it just providing easier management?
How do you protect the access clients?
All these topics are being discussed in this roundtable podcast. Well worth a listen.
Sound quality is not optimal all the way through the podcast, but it's still a good discussion.
Virtualization Security Roundtable, episode 73 "Virtual Desktop Security"
A VDI desktop is no More Secure than a Standard Desktop
The video here is the view from my bedroom window.