For lightness, µTorrent is definitely the winner for Windows. BitRocket seems to be the lighweightiest for OSX.
However, if you've only switched because of the crap they added with Vuze, as rabbit said, you can disable that. I won't be at all shocked if they end up disabling it by default in future versions, because of the amount of people that have stopped using it due to the confusion. I'd definitely say give it another shot; it hasn't actually gotten any more bloaty than it ever was, as long as you turn of Vuze.