I don't know about you but I just can't get used to browser tabs being on the title bar, it just doesn't feel natural to me.
If you agree and you would like to move the tabs back to where they were enter the following command in Terminal...
defaults write com.apple.Safari DebugSafari4TabBarIsOnTop -bool FALSE
Quit and restart Safari and the tabs should be where they were in Safari 3. To move them back again just replace FALSE with TRUE in the command above.
For more Safari 4 hidden preferences see this article.