I just did mine. I wasn't going to, since the plug was $60, but I had a trigger job done, and the smith said there was all kinds of crud blown back into the firing pin hole and action, which I had to assume was from 209 primers. I have the Katahdin short barrel 50 cal.
I've only had one range session, but it performed pretty much as advertised, I was getting 2.5" - 3.0" groups at 50 yards (5 shot) and haven't really worked with it much.
I was also working with a new red dot sight, which I find to be a little challenging with bifocals, so I think I can improve on accuracy.