I just got Windows 7 Pro loaded and after using MSConfig to disable unwanted startup items I found that there is now a way to disable seeing the reboot message.  After reboot however I found that there isn't a way in the MSConfig gui to restore that option.  After a search I found this link on these forums: http://www.geekzone.co.nz/forums.asp?forumid=45&topicid=34135 .  Unfortunately that thread is locked.  The answer to that thread and my problem is that you need to delete the following from the registry:

[HKEY_CURRENT_USER\Software\Microsoft\Shared Tools\MsConfig]
"NoRebootUI"=dword:00000001

Hope this saves someone else a few minutes.

Cheers!