Hi! After I upgraded Parallels from 7 to 8, I noticed there's a delay between pressing the cmd⌘ key and the Windows 7 Start menu pops up. Inside Native Boot Camp (which Parallels is using) the pressing of cmd instantly opens up the start menu, and I seem to remember the same thing happened in Parallels 7. Is this some new behavior?
Not that I used 7 for more than a week before upgrading, but how could it have ever worked differently? If you are using the setting to map the major Mac shortcuts like Cmd-x,c,v to work inside Windows, then those wouldn't work if the Start menu were in the way before you hit a letter key. Turning that feature off should leave you with clean key actions, plugging in another USB keyboard and dedicating that to the VM would definitely work correctly. I haven't been bothered much by the Start key, but have experienced similar quirks with Shift & Ctrl in games. (In mouse programming terms, the Single Click action has to leave stuff lined up for Double Clicking. If Double click were to open a file, and Single click were to delete it, then what are you even pointing at the second time your finger slams home against that mouse button?)
I fixed it with Sharpkeys I noticed the same issue, and here's how I fixed it: download Sharpkeys 3.5, and reassign the key you want to a key that you don't use as much... if you reassign Windows to "Alt" it will respond just like you would expect it to in a native/bootcamp environment.