I've had a set of 31 x 10.50 R15's for about 7 months and I've just gotten back form my 3rd weekend of wheeling with them. I am thoroughly impressed. A long time ago I ran a set of the original MT's and I am on my second set of AT's which I use for street duty. I can't really compare a lot to the old MTs since it has been so long, but the KM2s are definitely quieter than I remember.
I'm not sure what they cost since my wife got them for me as a birthday present, but she did get them from 4Wheel Parts with hazard without any problems.
As far as performance goes, I have tested them in rocks, sand, and mud and have not found anything that they don't do well. My first trip out it was very cold so the ground was basically solid, but I was able to climb out of some pretty deep ruts that I wasn't sure I was going to come out of. The second trip out I got involved in a debacle on a new trail that was basically a swamp and we had to climb a rutted out embankment to get out of. I was the only guy to make it out on 31's (a ZJ w/ an Aussie in the rear on 32 ATs made it once but couldn't make it out a second time after pulling someone free and a 4dr JK on 35 ATs made it out after me but everyone else took a winch). This last trip I was able to make it up a couple climbs that I didn't think I'd be getting up (
http://www.youtube.com/watch?v=0qkcfK71C3Q ) and I also had no problems on a mud embankment that a fellow XJ on 31 MTR's just couldn't make.
I'm definitely a fan.
