I've always been skeptical at using Mono and Moonlight. In fact, I've always avoided them if possible. Why? Because I really don't want any trace of Microsoft software on a clean GNU/Linux installation. Even though Mono is maintained by Novell/Xamarin and not Microsoft itself. I think that Microsoft had good intentions in allowing .NET to be available on multiple platforms, but I think Microsoft should have administered it directly rather than hand it off to a 3rd party. But, that would have required Microsoft to directly develop software for non-Windows platforms. I've used applications that rely on Mono and Moonlight, and have found that they aren't 100% compatible with Windows-based .NET and Silverlight applications.
Even recently I was looking to see what alternatives are available for Rhythmbox, a music manager program for Gnome. Rhythmbox is a great application, but it does crash here and there and I was looking for something that would synchronise playlists a little better than Rhythmbox does. Banshee was one of the top rated alternatives, but just as I was looking to install it I saw that it required the Mono (.NET) libraries. That was an instant red light for me and a showstopper for that one.
Just today I saw an article that mentions Moonlight (open source Silverlight) is being abandoned. The reasons were that Silverlight is not being adopted as originally intended. In the article, Miguel de Icaza states that with Silverlight, "there are just too many limitations for it to be useful.", and that "Microsoft added artificial restrictions to Silverlight that made it useless for desktop programming.". Here you are getting feedback at the core of development for Microsoft's supposed "love" for open source, where restrictions are doing more harm for the technology than good. The article also draws conclusions that Microsoft may be looking away from the .NET platform altogether, mainly for Silverlight. Silverlight maybe, but I doubt for the entire .NET platform.
Personally, this adds to my conclusions that .NET on non-Microsoft platforms was a half-hearted attempt right from the beginning. I think Microsoft is still learning that to be a true contributor to open source, it must dive in with good intentions. And from my perspective based on past and present actions, I don't see this happening anytime soon. There are too few products that Microsoft fully supports for non-Windows, that don't contain some sort of restrictions. Microsoft obviously dislikes the GNU GPL. But I have a feeling that if they were to release more products under the GPL as true free and open products, they might have a chance at being successful with them. Now the question is, where is the entire Mono project headed, is it doomed as well? Only time will give us the real answer.