I've had one for about three years now, and it's still my favorite gun. It's also my wife's choice for a house gun. I have a couple of 30 rounders that work excellently in it, as well as four factory 15 rounders. We stocked two of the 15's with +P+, which it handles with no problem, for home defense. I put one of the "One Ragged Hole" ghost ring rear sights on it, and it's incredibly accurate out to 50 yards. The triggers can be lightened up a bit, and some of that pre-travel taken up a bit. Let me put it this way, I bought the Ruger first. I have since bought, and sold, a KelTec carbine, which I liked, but it was a little cheesey feeling. I also bought, and sold, a Beretta Storm. Neither were the equal of the Ruger carbine. I have considered trying to fashion a .357sig carbine from a PC40 with a PC9 barrel. It should work, but I'm not sure.
My three main complaints with the PC9, for me personally are: short LOP (I added spacers to mine), it's heavy, and the integral Ruger scope rings. They work great on the 77's but you have to buy $50 mount to put on most red-dot's, which go perfectly with this carbine.
For the money, or not for the money, it beats the KelTec and Beretta, hands down. I'd only get rid of it for a HK94.