Hmm. The Mono project has decided to use winelib to implement System.Windows.Forms (the .NET UI library), rather than making wrappers for all the underlying windowing libraries.
Implementing a Gtk, Qt or Aqua based version of Winforms was going to be almost as complex as implementing Wine itself. So the new strategy is to only roll out a WineLib-based implementation. [Mono Project News]
This will have interesting consequences. Firstly, it will mean that the UI will probably be working reasonably soon on Windows, and secondly that .Net apps running on Linux will look like Windows apps running under Wine. Is that a good thing?