As you can see, I have five groups. The first is useful live tiles and (somewhat) commonly used Metro apps (Rain Alarm is cool; not only does the tile display the proximity and intensity of any nearby rain (there's none at the moment), it also uses the Win8 notification system to warn me if rain is approaching). The second group is less used Metro stuff (Bing and Travel are really only in there because they look cool ). The third is office and development. The fourth is games. And the last is other frequently used tools.
I spend 99% of my time in desktop land, and the really frequently used stuff from here (like Outlook, VS, OneNote and PuTTY) is also pinned to my taskbar. But it's nice to get an overview when I turn the computer on or press the windows key. And I've been training myself to click the Outlook tile after starting my PC rather than go to the desktop and then click Outlook on the taskbar.