I'm very impressed with the Parallels virtual machine, but I think disabling access to the os x environment while in the virtual machine is a step in the wrong direction. If I wanted a "pure" windows environment, I would use Boot Camp. At the very least, make it an option. By the way, I'm a paying customer, if it matters.
I want 'pure' Windows environment WITHOUT Boot Camp, so I'd rather not have that back.... that and I still can use Expose to switch around anyway. So chalk this one up as something that needs to be user configurable as well.
The reality is that they need to make all these keys configurable. They will never find a combination that doesn't break something for someone with "one critical app."
I definitely want an optional full-screen lockout mode, where as much CPU and keyboard resources are given to Windows. This would mean that Expose and Dashboard F-keys wouldn't work (and hence would work properly in Windows). I would also want the command/apple key to be mapped to the windows key, so that the windows-d and windows-l keyboard shortcuts work. In this mode, there would have to be a single, tightly defined way back into OS X that doesn't conflict with the guest OS.
And what I really want are all the modifier keys used by Windows (ctrl, alt, shift) to go through unchanged, the F keys to go through unchaned, but the Apple key to be completely masked from Windows so that Apple-tab, Apple-H, etc work. And NO key combo to make a right mouse click either, I already have a right mouse button thank you. As long as all these options are configurabale then all will be well. The way Virual PC handles this with a few simple simple options is pretty good.
Again, make it configurable This would be a complete knockout for me - I want the apple key to work as Ctrl in window so all the standard shortcuts (cut/copy/paste/save/selectall...) are identical. I'm saying this just to stress the point a bit that the only solution is to make it fully configurable. What is offered in the GUI for end users is disputable, of course, and must not get too complex. But the underlying implementation should be as generic as possible. The engine should allow passing or blocking any particular key combination, and should be able to map any modifier key to any other modifier key combination in the guest OS. And these mappings should be somehow available to be tweaked by advanced users - no problem if it is in some text config file.
