I had the 29er version.
During summer, I liked how the fork performed, after replacing the damper oil with some of a lesser viscosity. I found it handled small to large bumps, even decent sized (on XC trails) drops and jumps well. The fork had a nice 'bottomless' feeling to it. Riding in anything below +10 degrees (Celsius) I found the damping would really firm up and below freezing was like riding with lockout on. The fork was not any stiffer than anything else on the market (I've ridden REBA's, SID's and Fox 32's in the last 2 years). Also, the steerer tube separated from the crown, leading up to that it was creaking like hell. The company that fixed it under warranty said it was a common problem they had seen with the XMM's. And I believe them, a month later after shipping me a new upper assembly, it started to creak again. I had it fixed yet again and then sold the bike. I didn't have a overly great experience with that fork to be honest. Come to think of it, the few people I know that rode it didn't like it (compared to other forks). From my experience, I can't recommend purchasing an XMM when there are better models on the market IMO.