I know this is an older post, but I'm a new member who was searching for info on Ruger P90's, and what I have to say applies to many of the questions and comments previously posted. I recently bought a used P90TH. I've owned a Ruger P89 for about 6 years, and love it. I wanted a .45 in my battery, though, and chose the P90 over a Glock 21. Anyway, first time I took it to the range it kept misfiring. I called Ruger and they told me I needed a new extractor. The tech asked me if I thought I could install it myself (she said all I needed was a little screwdriver to pop the old one out). Ruger sent me the part (for free, of course, and I didn't have to send the gun in), and I had the new extractor installed in about 5 minutes. I noticed the old extractor was just a little bit bent. I took it back to the range, and haven't had a misfeed again. I love the P90 - the kick is only slightly more than the P89, and so now I carry it whenever possible. My groupings are pretty tight, although I'm consistently shooting to the left of center. Don't know if it's me or the sights, but it's consistent.
Anyway, my $0.02