I love the Apple Mighty Mouse. Except (as most users do) when it's time to clean the little scroll ball.
I'm not going to include all of the solutions (rubbing it, opening it) since most of them are posted on the web. From my experience, it's unavoidable to open it to clean it from the inside.
Unfortunately, this action means you have to unseal (or crack-open) your Mighty Mouse. This is a good instructable:
But instead of re-sealing using super glue, use a couple of thin pieces of scotch tape.
Super glue fumes might be damaging to the circuits, and it will leave your mouse stained and with bumps if you're not careful.
Also, you will need to crack it open again if you need to clean it up again.
Scotch Tape works like a charm and it will allow you to open it in the future.