Been using VP for years and been having the same issue. No matter the computer, hardware, or preview setup, performance is bad. This is because unlike the rest which uses real-time processing, VP processes all effects and what not, then encodes them for preview (at least that's what I can infer). Sadly I don't think they utilize hardware encoding which makes lives soo much easier for us. QuickSync and alike is very common today. Everybody should be able to duplicate the problem.