The one you linked to is not a locker, it is the "TruTrac" which is a Torsen style differential that uses a helical gear mechanism to vary the power based on which wheel has the most grip. If one wheel starts to spin, it will put more power to the other one to balance out the grip. They're pretty slick units and make no noise or chatter at all.
I have one in my Chevelle, but I never got it "broke in" before tearing the car apart. I only put about 200 miles on mine and 10 autocross runs. It was still launching a little crooked then, but I'm told it gets better as things wear in.
