ScreenSaverGracePeriod setting in registry

1) Is the ScreenSaverGracePeriod setting supposed to work in Vista, as in
?

We have a group policy that sets this REG_SZ value in
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon, and
it works in Windows XP, but it does not seem to have any effect in Windows
Vista.

I have tried it in:
Windows Vista Business SP-1
Windows Vista Enterprise
Windows Vista Enterprise SP-1
Windows Vista Enterprise SP-1 64-bit

As an experiment, I tried it at HKEY_CURRENT_USER\Software\Microsoft\Windows
NT\CurrentVersion\Winlogon and it seems to work. This may actually be a
better place to put it (a user setting), but is not documented.
2) Can I expect it to continue working?
3) Any idea if it will work in pre-Vista versions? (I haven't tried it
yet.)
4) Is HKEY_LOCAL_MACHINE\Software\Microsoft\Windows
NT\CurrentVersion\Winlogon\ScreenSaverGracePeriod supposed to override
HKEY_CURRENT_USER\Software\Microsoft\Windows
NT\CurrentVersion\Winlogon\ScreenSaverGracePeriod, or vice-versa?