I was in tears when my Logi G15 died on me. Since they don't make it anymore I settled for a G510s
I was in such dismay when Logitech discontinued their track-ball corded mouse, I even bought a Japanese unit that was nowhere near as good. My previous experience with the cordless version was that it was too fat and heavy. Imagine the joy when I discovered the M570! Been happily camping ever since.