Yep, that is a quick release for the shock. I get so tired of tearing up ball cups twisting them off the ball. Someone here on RCTech suggested one of these and I had to try it. I'm not sure if it is good or bad yet though for two reasons. First, I had to run the antenna / shock mount forward one hole due to the length of the quick release (and this changes my setup away from Jason's known setups), and two, the spring on the quick release applies a little pressure which might throw off the spring rate of the shock a little (I think I can account for it though). The quick release part works fantastically though.
I'm going to try it, worst case I'm out a few $$.