As someone whose work life involves a lot of C# development I can honestly say it's a great little language that would get used much more if it's name wasn't tied to Microsoft. Beyond that there's no doubt the Mono project has done some impressive things.

That said, I wouldn't do this on a commercial project. Because when a bug does come up you just have too many layers to contend with. Is it a bug in my code, in the Unity Framework, in Mono, in the device or what? This is a particularly significant problem when dealing with Open Source projects with very little in the area of support mechanisms and Apple which seems to think far too much of itself to offer decent developer support.

So in the end it's a nifty proof of concept but I personally couldn't bring myself to trust it.