Maybe I'm a Luddite, but..
..I don't get the benefit of "tabbed browsing" or "tabbed email". Personally, I'd like my web pages to open up in several windows, so that I can click on the bar at the bottom of the screen, see all of my options, and go to the correct one right away. The difference is that if the pages are in different windows
, I can see the title bar of all of them at the same time, by clicking on the Firefox (or whatever) tab at the bottom. If they're different tabs in one window, I can't do that (and, if I have a lot of tabs, I can't even easily figure out which is which in the tabs (because they scroll off the screen).
And now, Thunderbird 3 has "Tabbed email!" Like it's the most awesome thing ever that people have been clamoring for. All I see is screen real estate for the tab that could have been used making the message panel bigger.
I guess I'm behind the times. Someone pass me a punch card..