I've had and returned the Magic Mouse about 4 times now. I want to love it as the scrolling is great, but for whatever reason my hand just enjoys a normal logitech mouse in concert with BTT to get the buttons/side scrolling/etc to do things I like.
My main issue with the Magic Mouse is the lack of height - I don't "claw grip" a mouse, but I do like to have just a bit more shape/height to help me quickly and easily, without looking, perfectly grab and start using the mouse. Over the course of day I'd always notice that the initial "grab the magic mouse and start doing something" experience just had a touch of orientation lag and would tend to move the cursor a bit etc.
Also, on a normal mouse, though I love gestures in general, I really prefer the super positive actuation of an action that a click provides. I'm very experienced with gestures and pads and no matter how much I tried, I'd always have failed activations of a gesture on the Mouse (not so much on the trackpads ever though).
I have a feeling a force touch mouse or some other updated version is coming that perhaps will have even more updated touch recognition hardware built-in. That might help, but ultimately the small area with which to actually do the gestures is likely the larger problem.
Glad some love it. It's very sexy looking and the scrolling is wonderful, but at the end of it all, a more normal mouse with some BTT triggers setup simply works more efficiently and comfortably for me.