The article is covering features in C# 3.0. Mono is perpetually playing catch up to Microsoft's implementation and according to the Mono site the "Mono API today is somewhere in between .NET 2.0 and .NET 3.5". Besides the fact that the language implementation is behind, developers also have to deal with the fact that the standard library isn't 100% compatible either. It seems pretty clear that C# developers that are not on Microsoft's implementation are basically second class citizens. I don't think Mono can be taken seriously if we're talking about being compatibility with Microsoft's implementation. It's not all bad, though. Mono seems to be a perfectly good platform when evaluated on its own.

That said, I have little experience with Microsoft .NET and Mono so these are the observations of someone only casually acquainted with either project. Can anyone here share any experiences with Mono?

Agreed. I personally think it's not the risk to put yet another layer in your stack that has the potential to royally fuck things up.