I'm asking it like it's a bad thing, because how many times I could read there that it's a cancer like flash, pdf and whatever little things. But I just checked yesterday, and it exists for Windows too. And intended for actual use, unlike something like Wine on Windows. And you can even bundle the runtime or bury it in your .exe program.
There are many "one true way" to develop things that work everywhere : java, python, web/javascript, some older things and some newer things I'm sure. But if I want to get started to do little projects, have to pick something. Web would be nice, but maybe I'll never have a smartphone to run little web apps on. My calls and positions are already tracked just by owning a dumbphone.
Back on point, one of the early posters said how he uses C#, and it would probably be a nice fallback / somewhat default language to do semi-system stuff, networking, multimedia, imperative programming.. or gasp, a GUI. What would draw me then is the F# language, and I know its parent language a bit (ML family). It would be awesome to be able to do actual useful stuff in that language (thanks to .NET libraries/infrastructure and some additions or sugar in the language) and if worst to come (i.e. something where functional programming is pointless or gets in the way) I'd use C# or whatever other language supported in the Mono CLR for those parts?
It's 2014 too and maybe Mono is better in 2014 than in 2009 or 2007.