GDI+ is very slow, almost entirely software whereas GDI is highly hardware accelerated. GDI+ is what the Graphics class uses on WinForms and it's just too slow.
Has anyone made a .NET GDI library so we can have the speed?
[EDIT] Many people are recommending OpenGL/DirectX. A requirement of mine is client compatibility especially remote desktop. AFAIK remote desktop does not support OGL/DirectX out of the box.[/EDIT]