Up until two days ago, I would not have been in a position to even enter this conversation. However, having owned a wired Mighty Mouse, I now have an experience-based opinion on the matter:
Frankly, it sucks.
Why do I say that? When optical mice were first introduced about 8 years ago, one of the issues they had was with glitches in the tracking technology. The mice had issues tracking on certain kinds of surfaces; also sometimes the cursor would spuriously jump to some other location and you'd have to find it and bring it back to wherever it was that you were working.
Now, over the years the industry has made significant improvements in the optical tracking mechanism that's used. Heck, for that matter even Apple's "Pro Mouse" contained those improvements. However, their Mighty Mouse seems not to, although I can't for the life of me explain how that would be. It does (well, did) all the stuff that older-generation optical mice used to. I have tried several different mouse pads, no mouse pad at all (of course then it's on a wood-grain surface), etc. No luck no matter what I tried.
I returned it to CompUSA and bought a Logitech MX400 laser mouse, with which the moment I hooked it up I was a thousandfold more satisfied with it than the Apple Mighty Mouse or even the Microsoft 6000 Laser Mouse which I had attempted to replace previously (I just wanted to get any and all of the Microsoft junk off of my desktop.)
One of the other things that irritated me (and I kind of knew this would be the case going in, so it was by no means a surprise) was the pair of buttons Apple placed on the left and right sides of the mouse, right where I would normally grab ahold of it. I tried to use the mouse with them enabled but had to pretty quickly go and shut them off.
Except for the PowerBook 5300c I owned several years ago, I have never been as dissatisfied with an Apple product as I was the Mighty Mouse.