I experimented with a PPQ for the better part of a year before I discarded it in favor of the VP9. I installed Trijicon HD sights on my PPQ - they use the same adjustable detent system as the stock sight.
Definitely a unique way to install a rear sight - on the one hand it is nice to be able to swap sights without a pusher. On the other hand, I wondered how well this system would withstand abuse.
That adjustment feature bugs me. One thing to push something and pop the SIM card out of your phone, but the rear sight in the dirt and out of zero is a whole different thing.