I just tried this for the first time, it's really good!
Something i noticed was that the audio in Dub mode gradually gets further out of sync as the film progresses. most noticeable with long videos (e.g. the shrek "muffin man scene" pack which has 62 lines). Seems that the video keeps playing but the sounds get delayed by loading or something - so by the end, they were about 5 seconds late.
Another thing I noticed was that the game can freeze briefly whilst playing or recording,which messes up the waveform drawing. I didn't notice this after switching to the compatible version, though.