I didn't understand the point of tabbed browsing when I first switched to Firefox.

But now I love it.  I use it as a way of keeping organized.  I often have dozens of Web sites open at the same time.  Tabbed browsing allows me to sort of stack them in piles, the way you would papers on a desktop.  For example, I'll have a window with news stories open, a window with my favorite sports message boards, a window with DAZ threads, one with Rosity threads, etc.  Each window may have two or twenty tabs in it.  Trying to sort through that many windows on the taskbar is a PITA, but sorted via tabbed browsing, it's easy.