Re:Mono provides the illusion of portability (Score 1)

But at the same time, if developers are targeting .NET under the illusion that they'll get easy portability, then there are probably better solutions. QT comes to mind, not to mention Java.

At that point, what's the advantage to using an interpreted language over a nice C++ framework like QT?

I don't have to recompile and maintain compilers for as many systems as I want to port to? I can stay in my preferred environment for developing the software and just distribute to the other platforms?

Seem like good reasons to me