I agree the mouse is nice, very Apple-design, but not perfect.
I'm too often left-clicking when I was planning to right-click - which results in double-clicking, or losing selection, or whatever else... -.
And then you start far-right-clicking, which means reaching very far on the right and putting some useless tension in your hand in order to ensure a proper right-click.
After playing Warcraft III for one hour last week (and quite many clicking errors), I got the painful tingling in my hand and forearm for the whole night, which raises the fear of RSI. Working in a fully computerized environment at work, the subject of RSI (by extensive use of mouse etc) is a subject of real concern. If in doubt, google out for the carpean tunnel syndrome etc.
Concerning the side buttons: never used, never will. You need to change your whole grip on the mouse to use them.
I think I'll go back to my previous mouse: MacMice, The Mouse. A close design to Apple's, with two real buttons and a wheel. Update: done.
It's a wired mouse, which I like better for photo edition. The previous BT mouse of Apple didn't satisfy me.
However, models from Logitech are really good, also in wireless.