"You might be asking yourself, "Isn't there already a G5 available?" Yes. But this mouse is newer and more improved than the original G5. The original G5 is silver with orange sprayed in the middle of the mouse; the new G5 utilizes a unique black and blue color combination. The USB report rate (how many times per second your mouse sends its position to the software) on the new G5 is 1000 reports per second compared to the original G5's 500 reports per second. Logitech also added a tilt scroll wheel to this mouse giving the user more ease of use and freedom. You may have already noticed that the new G5 has one more button on it's left side. In the Logitech software, I customized the smaller button on the top to cruise up, and the bigger one on the bottom to cruise down."
FULL STORY @ OVERCLOCKERSCLUB (http://www.overclockersclub.com/reviews/logitechg5/)