As VMWare Fusion RC1 started supporting Global keys, which was handy for me to switch between two desktops using Virtue desktop manager as I keep one desktop for Fusion Vista in full-screen mode and another one for Mac OS X. Switching between them when Fusion started supporting global keys is easy (CTRL + ALT / OPTION + Left or right arrow).
Actually this is well needed feature that I was expecting even in my 10 wishes to run Windows on Mac. But actual problem started when I started using Visual Studio 2005. As Visual Studio is my default working environment for most of the C/C++ projects that currently I develop, the editor becomes unusable as F and CTRL + F combination keys are treated as global keys by Fusion and invokes Mac activities. So, I can not even do a search using shortcut keys nor debug a program(F5, F9, F10..). So, I have to manually turn them off in Fusion (Menu -> Preferences -> Uncheck Enable Mac OS Keyboard shortcuts) inorder to get the visual studio to work. So, currently am back to basic without Global key support in Fusion. I know that Parallels supports this global keys, not sure how it acts if another application within guest OS has the same key combination. I still think Fusion should first give the preference to local guest OS and then pass it on to host OS instead of directly to host.
If you’re on a laptop, perhaps you need to hold the Fn key down while you use the F1, F2, etc. keys.
If they’re assigned to some other app, you can go to System Preferences -> Keyboard & Mouse -> Keyboard Shortcuts and disable them.