My present bow, a Martin SlayR goes on the scales at just over 8lbs, but it is rock solid once I get onto my aiming point. I can shoot more relxed and accurately because I don't have to tense arm muscles to physically hold the bow still.
I was actually thinking just the opposite, since my bow is heavier also, I was thinking a lighter bow would reduce the amount of movement because of being easier to physically hold extended. My hunting area is heavily wooded so not alot of wind problems