If you are switching to cantilevers from vbrakes you will also have to change out your brake levers (and if you are running all in one brifters that will be difficult). If the brake levers and shifters are separate you could try upgrading the levers to avid speed-dial levers. These levers have the ability to control how stiff or spongy the feel is and may reduce the problems you are having. This upgrade probably made the biggest difference (after good pads) in performance when I used to have V-brakes on my mountain bike. I also wonder if there is something with how your cables are setup that is introducing a lot of flex into your setup (compression-less housing, bracing for anything that flexes, etc).