In the Safari 4 betas, the tab bar was moved to the top of the window, rather than underneath the address/bookmark bar:
Is there any way to get this back in the current Safari 4.0.3 (non-beta release)?
I can only find the command to disable this feature in the betas:
defaults write com.apple.Safari DebugSafari4TabBarIsOnTop -bool NO
YES has no effect with the current version.