re: Not sure what tabbed browsing actually is.
If you are still using IE6 (which I rolled back to) you do not have tabbed browsing it is a feature of IE7 beta. It is also a current feature of Foxfire and Opera. It is not the tabs in your task bar. They appear on the bottom line of your browser tool bars
Basically it gives you the option to open links and other websites in a tab instead of a new window. You can have a lot of sites open at the same time in other words and just click the tab to view the site.
By the fact that all the major browsers are including it, I assume it is in demand. I have just not found it useful.