WinForms 2.0 for Mono is Code Complete
After four years of work, Mono finally supports all 12,776 methods in the WinForms 2.0 API. Weighing in at 115,000 lines, there is the possibility for bugs.
WinForms isn't the only GUI toolkit available for Mono developers. While WinForms is suitable for cross-platform projects, Mono is also working on libraries that have a closer match to the native GUI. These include Gtk# (Gtk+), Cocoa# (OSX), and Qyoto (Qt/KDE).