out of so many movies i've played with xtreamer (mostly 1080p, some 720p) 4gB-25GB in size, i only encountered about 3 movies which stutter. But that's only a portion of the movie, i haven't encountered any movie that stutters to the point of being unwatchable. mind you, we've played close to a hundred movies already.
i agree with scifi-fan, when a movie stutters, chances are the file is at fault not the player. at just a little over 5K xtreamer is the best nmt for the money if all you need is play HD videos. now, if you start looking for dts-hd, torrent downloader, among other features, that when you should look at the more advanced NMTs like pch a200, c200 and others.