Very exciting news! SMP and OpenGL 2.0 support just about double the value of VirtualBox for graphics programming.
VBox uses OpenGL passthru, which has a measurable performance penalty. Unfortunately, it doesn't really make sense to benchmark the current version (which only support GL 1.5). Once VBox 3 is out, I will do some extensive performance tests - I don't expect it to be a speed demon, but I hope it will be usable for general graphics programming.