The company that made the centerfire Quik Shok ammo (Triton) went under. I keep hearing rumors that another company has or will produce centerfire Quik Shoks, but I can't say for sure.
The rimfire Quik Shoks were made by a different company, and are currently offered by CC!.
The only animal I ever shot with one was a rabid Racoon, and the results were pretty impressive.