The mouse distance issue doesn't really bother me. Something well over 90% of the time, I switch tabs using keyboard shortcuts (actually, most of what I do in the browser is now keyboard based, thanks to Vimperator http://code.google.com/p/vimperator-labs/ ).

One thing I'm curious about for the mac is whether full titles on the very top will still be displayed if the tabs are on top. In Chrome, if I go to a page that has a long title (including this comment page), I have to hover over the tab to get the full title. Otherwise, it just shows up as "Hacker News | Why Tabs a...".