I like to use it two-handed, but you could theoretically use it with one. I just have tiny hands. It is possible that you could end up lifting it, but I'd say it's at least a few lbs. I'm positive it could be used as a murder weapon.

As for buttons, I always wondered what the difference was in the higher priced models. There are actually two versions of the SpaceNavigator. One is for personal use, and the other is professional. That's the only difference aside from cosmetics. The rest of them are like tablets in that you pay more for more buttons.