i think there is a new revision of the G5 that has an extra button on the side, a big plus since the original only has one. the only grip i have with the g5 is the wheel is too 'clicky', after awhile it has a cheep feeling to it, but i can say it still works great and overall the mouse is bulletproof. i bought this used and beat up, used it for a year, still going prefect.