I have one and love it as well. A giant modern trackpad in all its gesture-interface glory is a pretty awesome experience. I still like to use a mouse for precise tasks, but for web browsing, documentation reading, and general use.. it really can't be beaten.

Try watching an experienced multi-button mouse user. They don't have to reposition their hand three times to cross the screen, or wait 300ms between every action for the gesture recognition algorithms to time out. Watching my coworkers pause all the time with their magic touchpads was very jarring for someone used to a more seamless flow of thought into action with a mouse. They probably don't even realize they are pausing, rather just subconsciously trained to avoid gestural misdetection by working more slowly.

Apple's defaults for cursor speed have always been really slow, which is sad because their trackpads are some of the few that are precise and accurate enough to work well with high sensitivity settings.

Ya, I basically need to use my Magic Mouse while my MBP is plugged into an external monitor and I'm not using the trackpad.

Not having easy access to gestures slows me way down while working.

If I want to play a game in Bootcamp, I just use a standard two button mouse.

Nthed. It's not great for all use cases, and it feels a bit slow when you switch to it, but after a few minutes you'll be going almost as fast as with a normal mouse, but with much better ergonomics and with full access to gestures and inertial scrolling.