I fully agree with Eteocles. I hate to sound like one of the elitists, but especially while multiboxing I don't see how you can survive without using your keyboard. The ability to have the different mappings and then effectively using modifier macros (making a single macro do different actions on shift/alt/ctrl etc) is just too great when doing something like this.

Also, about the mouse clicks, I believe I've seen keyclone mention a few times that even across multiple machines he doesn't recommend using the click to pass as it can be unreliable or something... I can try and dig up a reference thread, I don't want to put words in his mouth.