Even I was surprised by the size of the thing when I took it from the box. It's tiny. One point about the device itself - a USB port on the front may have made sense, but I understand it would affect the asthetics of this beautiful piece of design.
With my PC, I'm in the habit of running a ton of programs at once; a top-end machine gets you into that habit. The Mac Mini is not a top end machine. I got the version with the faster processor and 512 megs of memory but I still have to be careful not to run too many things at once. If I do that, it's sweet as a nut mate, sweet as a nut.
Highlights so far include Dashboard, Spotlight, the dmg installation process (drag and drop to install). I'm still in a slightly confused 'mid-switch' state though...