I love programming with .NET, especially C# 3.0, .NET 3.5 and WPF. But what I especially like is that with Mono .NET is really platform-independent.
Now I heard abou
From the mono website
At this point, the Mono project does not have plans to implement Windows Presentation Foundation APIs as part of the project.
Moonlight is an implementation of silverlight, which is a browser based flash like technology based on a subset of WPF.
In my opinion the choice to not implement WPF is monos biggest mistake. As WPF is fast becoming the default choice for new .net user interfaces. See this blog for more.