From what I understand, motionflow is entirely pointless when both watching Blu-rays and playing video games, it is only useful when watching TV broadcasts, especially sport, to improve the quality of fast movement. This is because it works by creating interpolated additional frames and inserting them between the existing ones to smooth the movement. However, despite what some people (it is a personal choice) and marketing might suggest, it is actually detrimental to watching Blu-Rays. This is because one of the main advantages of Blu-Ray is the ability to display film content at 24 frames per second, which is what the film is natively recorded in. This results in Blu-Rays looking more authentically filmic than DVDs, with slightly jerky film-like movement which is how it should look. However, if you are using motion plus, it will add extra frames in, increasing the frame rate and negating the filmic look, making the image smoother but look more like video than film, which I find undesirable.
Additionally, by adding extra frames to games, you increase the latency (lag) of the screen, with obvious bad results when playing games where reaction time is important.
Ultimately, its for those reasons that I chose a set (see sig) that didn't even have motion plus, as I considered it a waste of time and money. Its up to you when and how you use it, but I would advise unless watching TV or maybe DVD to leave it off, especially on Blu-Ray and games.
Hope that made sense and helped!
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