Using a magic mouse is near-instant wrist pain for me. Although I like the idea of gestures on the mouse, it just won't work for me. On the other hand, the logitech MX ergo has been stellar for me for the past year!
Same for me - I can use almost any mouse going just fine, but any shade of the Mighty Mouse feels instantly painful to me.
Also, on the original Mighty Mouse I used to use, I frequently found however hard I pressed, I couldn't click it - my hand just didn't correctly align with where I was supposed to apply pressure.
I swear by the MX Ergo, but I splurged on a Ergo M575 late last year, and while I don't love that it only supports a single device (unlike the MX, which can switch between two), having an even flatter trackball is nice.
Also, on the original Mighty Mouse I used to use, I frequently found however hard I pressed, I couldn't click it - my hand just didn't correctly align with where I was supposed to apply pressure.