I upgraded to 2.1.1 only to end up with kernel panic at the next startup. Back to 1.5, then tried again 2.1.1. and again ended up with kernel panic at startup. Went to logitech.com to see what's going on and sure enough found 2.1.2 (posted there on 12/21/06), installed it and it works flawlessly as advertised. Though I'm still working with my keyboard/mouse duo (am waiting for my VX revolution to arrive), thus, can't comment on the potential issue of recognizing the new mouse (17"PB, 10.3.9).