"But it's kind of unsupported and most of the time it lags behind. Currently on my brand new ubuntu system, it's version 3.2, on my "stable" ubuntu its 2.10. The current version is 3.4."
Isn't that more of a problem with Debian/Ubuntu than it is Mono? You're not comparing what Mono's released to Microsoft's .NET runtime, you're comparing what Ubuntu ships to what Mono themselves have released.