I bought both the Magic Trackpad and the Magic Mouse to use with my MacMini. Both of these replaced a wired Kensington Trackball. WIthin a week the Magic Mouse earned a place on my storage shelf along side the Kensington Trackball.
I own both as well - got a "refurbed" MagicMouse for 1/2 off and the MagicTrackpad for my birthday. I move back and forth between them on my desktop most of the time using the trackpad but somehow when I'm using Photoshop the mouse just feels more right.