trying to figure out how to use App Switcher on Lion
Use the Mouse System Preference. There is a setting for each button on the mouse - including the nipple like one on the top. On my iMac I have this set to Off, but there is an option for Application Switcher, which if you chose that it would allow you to switch application by clicking the nipple button. I just tried this and it works, though I might not leave things set this way. If you don't like the idea of a nipple button, it's also called a mini mouse button. Oh, I'm using Mountain Lion too