Want to know what my least-favorite mouse is? It's the round ADB Mouse II. Want to know why? Anyone who's had these things for years on end ought to know that the clicker, the mouse button, goes bad after a time. It gets to where you need to apply extra force to keep it down, so you'll end up dropping icons or having a menu roll up prematurely. I have about 4 or 5 of these mice, and only 1 has a good clicker.