I think it is worth adding OpenGL preview as an alternative to the SreeD software renderer, but people should keep in mind a few limitations. First, this would be a realtime preview system, and would not affect final render times. Rendering engines for final images are nearly always software engines. Graphics cards are not architected for doing things like raytracing. Although there are some experiments out there in trying to offload some raytracing math onto GPUs, there isn't much beyond experimentation happening on this front. OpenGL cards could probably generate a render as good as the P4 scanline renderer, but its not going to do everything that firefly or another hybrid raytracer is going to do. Also, regarding speeding up the preview display, OpenGL acceleration will speed up rotation, translation, etc., of fixed meshes, and certainly camera view changes. However, posing (where you are actually changing the displayed meshes) will probably not see as large of a speed boost. All that said, I think it's still a good thing to add as an optional display mode.