Yeah, as johnbt says, they're a great little gun *FOR WHAT THEY ARE*. It's a real handful to shoot for me, and not a lot of fun - but when I want a full 9mm in a mousegun-sized package, I grab my R9.
Changing the recoil spring is simple, and inexpensive. I change mine after a hundred rounds or so - about once a year.
Mine will feed anything dependably, so long as I do not limp-wrist the gun. If I get sloppy with it (shooting it like my larger semis), that's when I have problems, and that seems to be the case with most people.
In short, I love it - for what it is. But in truth most of the time when I want a pocket gun, I reach for my 642 - which I just shoot better, with my big hands. Still, when I need a super slim gun in a reasonable caliber, my R9 gets the duty.
Jim D.