I had completely ungainly problems with my Mighty Mouse. At the outset of the installation process, I faced a huge screen that was telling me to replace the batteries in the mouse. Never mind that the mouse was working fine under 10.4 and that the batteries were fairly new. I changed them anyway. Installation proceeded. After install, on restart, the Bluetooth manager showed up and bitched about my not having a mouse it could find. I tried a few things, none of which worked, then replaced the batteries again with the ones I had in originally. Now it works. That's just funky.