stock bar weighs 13lbs. As far as it helping on launch, disconnecting the end links will allow the suspension to be able to rise more and put more weight on the rear. Now this also depends on your suspension setup in the first place....
on a stock or loose front suspension it will help, but on a stiff or lowered suspension it won't that much.
It didn't help at all on my car, but I have Steeda Super Sport springs and bullitt shocks/struts so it's lowered and stiff. I cut 1.6 60' with the bar on and off