The only concern I would have is that Microsoft might try to crush Xamarin at some point, but I wouldn't count that likely, Mono is their ticket to keep .net from looking like anti-competitive platform lock in.
I wish I could go on but I've had this argument before.
Microsoft is not setting technical direction for Mono, and I expect that there are few (if any) Microsoft employees contributing to the project -- because of conflict of interest and IP concerns. They are very much at arms-length with regards to Mono.
So far as *nix tools being superior - I would agree that they do what they are designed to very well. But don't turn up your nose at C# and the .net framework -- it's quite good, and doesn't have the Java factory factory factory issues.
It isn't. Try developing apps with it. Then compare it with Java or Python. You'll see the light eventually.
> The only concern I would have is that Microsoft might try to crush Xamarin at some point, but I wouldn't count that likely
Microsoft is a beast. They are currently making more money from patents licensing for Android than they are from Windows Phone. Wishful thinking has no place in this world.
That doesn't mean that Mono is any more of a risk than the alternatives. Oracle sued Google for Java, right?