I've documented a new Windows 7 feature called Guest Mode (originally it was called PC Safeguard) but my most trusted source close to Microsoft tells me now that this feature, sadly, has been permanently removed from Windows 7 and will not appear in the RC or RTM versions of the OS. (It had been missing in action from the previous several interim builds we've seen.)
RIP, Guest Mode.
I will update the Windows 7 Feature Focus section accordingly.
Related: I'm also told that Microsoft will not be releasing a Windows 7 variant of the Steady State/Shared Computer Toolkit any time soon to compensate. (Guest Mode was based on this technology.) That doesn't mean that one won't happen eventually. But it's not in the schedule right now.