Microsoft Windows vs Linux vs Mac OS X

Simply stated, below are my perceived difference in Windows XP vs Windows Vista vs Windows 7 vs Linux vs Mac OS X on the User Account Control (UAC) issue from the standpoint of one who has them all installed in production use:

1. Pre-XP and Windows XP – unmanaged default installations have administrative (root) privileges, not good as we’ve seen; you can create unprivileged accounts and system changes will require administrator login (with a right-click clue on what account has it);