Today, I stripped the last references to System.Windows.Forms from OpenTK.dll. System.Windows.Forms is now confined to OpenTK.GLControl as it should always have been and the result is a leaner and meaner library that should start up just a little bit faster than before.
Next step: remove System.Drawing from the core library. With the exception of System.Drawing.Icon, this is trivial - in fact, there is a sysdrawing branch that does not require SysDrawing at all (yeah, I like oxymorons). Unfortunately, this change blows API compatibility to pieces so it will have to wait for a distant OpenTK 2.0 release.