I've succesfully gotten OpenGL working with Windows Forms under Mono. It works quite well, and i'm surprised at how complete the Mono WinForms implementation is. The only thing I couldn't dupicate in Mono from the native .NET version was MDI. It works, but it's really buggy, so I replaced it with a tabpage system, which I'm actually starting to like better than the MDI design.
Anyway, here's a screenshot of the (incomplete) Mono version of Clockwork running on SuSE 10.1 (x86-64).