I shot mine yesterday for the first time, it was great. 288fps with compressed air at the chrony.
900 rounds no breaks or problems. switching over to firststrikes with he thumb screw is fairly easy. although the performance of the FS rounds was less then stellar. any hits I did get with them didn't break.
2 of my teammates also shot theirs, but one thing they complained about was when they got nervous and began shooting fast(auto-triggering) they had a blast of air when they slammed the pump back.
while I was cleaning mine I realized the hammer connects to the blot long before the pump arm screws reach the back of the slot.
it looks as if the part of the powertube that the hammer hits could easily be an 1/8 of an inch towards the threads and still open the valve fully, but allow the pump stroke to collect the hammer with out slamming the valve open on the back stroke. I guess I will be messing around with a few different power tubes to see if I am right.
I am a life long Nelson base shooter, so I don't normally have a issue, but people coming from Sheridan based guns are use to being able to slam the pump back as hard as they want with out any ill effects.