FWIW:
I didn't like the tabs on top with Safari beta 4 and I found a post by Marvin on 02-28-2009 that suggested this site:
http://www.tgdaily.com/content/view/41555/140/
Under that site, I found the following article. It put the tabs in their "regular" position. I tried it and it worked.
I don't know if this would work to put the tabs on top for Safari 4.0 or not, but someone can try it - maybe with some possible modification.
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Users running Safari in OS X are in for a treat because they are not require to edit the com.apple.Safari.plist file directly. Instead, you change preference setting with commands invoked in Terminal. For instance, to move the tabs bar to its regular position, you simply type the following command in Terminal (NOTE: The text here should be input on one line, it is divided into two lines for display purposes only):
defaults write com.apple.Safari
DebugSafari4TabBarIsOnTop -bool NO
Consequently, to move the tabs bar back to window's top, you need to change the value from NO to YES by typing the following command in Terminal.
defaults write com.apple.Safari
DebugSafari4TabBarIsOnTop -bool YES
*
If you want to set a preference setting to its default value, simply run the defaults command with the delete flag for a wanted preference item. In case of above mentioned tabs bar placement, you would type the following command in Terminal:
defaults delete com.apple.Safari
DebugSafari4TabBarIsOnTop
*
Note: The defaults command doesn't require you to include the -bool NO part.
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Maybe someone could try this in reverse and let us know if it works.
If it does work, the credit goes to Marvin. If it fails, blame me.