Well, I'm still using a Microsoft mouse I swiped from college when the cheapo wireless one I bought to replace my third broken Mighty Mouse broke, and I don't plan on changing anytime soon. The MS one is nothing fancy, simple two buttons and a scrollwheel, but it fits my hand perfectly, doesn't need feeding with batteries, and, well, was free 🙂
I like the look of the Magic Mouse, but can't justify spending £55 (or however much it is) on it.
Plus, being a drummer, I tend to tap along to whatever I'm listening to on the top of this mouse when my hand is just resting on it. I've got it perfect so I can tap adequately without accidentally clicking. I'd be concerned that the Magic Mouse would be sent mental by my constant tapping. 😛