I dont have Star Trek so I cannot try that clip and I see no noticable jaggies on any films when I've looked for them, even on my 8ft screen which brings out the worst in most things. The difference between the HTPC and proV-DVD is mainly that the proV setup loses out slightly on edge detail ( its just a liitle softer) and if you look really hard the HTPC is perhaps marginally better focused (probably the shimmering you mention) but hardly blow it away different.
My opinion before I compare the PS DVD is that on the ae100 with its 480 line res and NTSC the difference between the HTPC will be vertually indistinguishable and mainly due to marginal differences in the setup (brigtness/contrast/gamma etc) more than a difference in ouput quality, so I agree it will be better than the proV, but not much.
I'm looking forward to the chance to compare though and also to get Technophobes opinion on my setup because the longer you watch the same thing you become acustomed to either what you like or dislike about it and if comparing stuff....notice the bad, but if watching a film...get on with enjoying it.