[dk75]

Are you saying that 69fps 1080 decode capability is to slow to playback smoothly 30fps 1080 actual movie?
My ION box is at least 2 times slower in VDPAU test than your and still I have smooth playback.
Your box is fast enough to have mixer temporal spatial + ivtc at any Bluray material and it is not enough?
I know, maybe with older drivers I twas like 20% faster but still, it is not a major issue for jumpy playback.

Did you tried to omit PulseAudio for playback?
I don't say to kick out PulseAudio because Ubuntu is too much integrated with it, but playing back with ALSA plugin in PulseAudio solved my jumpy playback problem.