Yeah so i have both... and i cant decide which i should use and which i should sell. The mighty mouse is bluetooth and the arc has a dongle which kinda sucks, but the arc seems smoother and more comfortable. The mighty mouse obviously has the right and left click which has a bit of a learning curve. The trackball beats the arc's wheel. Both are customizable (intellipoint compatible), but the mighty mouse can sometimes be hard to get working on non-macs. So what do you think is better?