I have the wireless version, not quite as light as the wired one due to the batteries but still lighter than most. The extra buttons are a bit futher foward than mice such as the original Intellimouse Explorer. The vertical scrolling is an absolute pain in the ass though, it is way too fast and I can't slow it down anyway, even with acceleration disabled and the speed set to the slowest it still scrolls about 10 lines at a time. Also the middle-click is very hard to push compared to some mice (all new MS mice have this problem). It also has horizontal scrolling which has limited uses. Call Microsoft a software company but they can't even figure out how to let people reconfigure the horzontal scroll, intellpoint, the mouse software can become a pain, such as warning you about low battery when you have a few days left of use.
Overall it's a decent mouse, it is quite a bit more accurate than optical mice which is nice. The main problem with it is the scroll wheel's stupid scroll speed, changing a weapon in a some games is a nightmare, you can scroll through 5 weapons in 1 movement.