I've been able to watch 2 movies recorded from the M-HD movie channel ("Prime" and "10th and Wolf"), beginning to end, stutter-free. Neither one was in 5.1 sound. But as soon as I try any network HD program (CSI, Amer. Idol, Grey's Anat., ... all in 5.1 sound), I see freezing constantly - at least once every 2 minutes and sometimes more often.
So, for me, the stutter is not on all HD playback, it depends on the program. I don't know if it has anything to do with whether or not the show has 5.1 sound yet or simply what channel it's on. I'm going to try a few 5.1 M-HD movies and see what I get.
I also have both HDMI and component video connections in place (with optical audio to AVR for 5.1), which never caused me an issue before, but I'll try disconnecting the HDMI to see if it makes any difference.
It's no consolation to me that I can watch some content stutter-free. V149 has 100% introduced a stutter/freeze issue which makes watching many prime-time HD recordings nearly intolerable. I can watch these shows stutter-free only if I watch them "live" ... but, hey, maybe I'll see some really good commercials, huh?