here on a PowerBook 800MHz and a Dual 1Ghz Quicksilver. No problems whatsoever. As for being scared to update a machine; you *should* be if you are using your machine for mission critical work. It is laughable to say that anyone should be more afraid of one OS's update than another. When you are messing with the foundation of your computing experience, THINGS CAN GO WRONG! No software is perfect, and anyone who tells you differently probably has a bridge to sell you.