The multi-touch features on my MacBook Air are great. Although, I mostly switch apps with keystrokes (Command-Tab) and/or Quicksilver, I wanted to make better use of multitouch when I could. You can activate app switching with a four-finger left/right swipe, but the navigation of picking an app and then making it active can happen in a few ways.
You can pick an app by either moving the pointer with a single finger to hover over the app of choice, or by sliding two fingers (left/right or up/down) to move the activation selector over the available apps.
You can select an app, though, apparently only by clicking the mouse button. This is what I found annoying. I hoped I'd be able to tap the track pad to activate the selected app. After some experimentation, I found out you can activate an app with a single four-finger tap, but not with a one-, two-, or three-finger tap.
Happy swipe-swipe-tapping!

