I get heavy CPU useage, the display on the front of my HTPC varies from 30-80% on TV3. However the picture is fine, no freezing or drop outs etc. I get the occasional mediaportal crash but not very often. I don't get motion blurr. Everything seems better since i turned UAC off. I run the powercinema codec, but get similar results with ffdshow. I wish hardware acceleration worked, however mediaportal runs fine. I actually wonder if I would be better off running GBPVR, as I think that be more compatible with EVR. At one stage EVR did work with mediaportal and i was getting around 20-30% on TV3, however EVR now makes my computer crash.
I imagine that mediaportal / vista / evr / ati will eventually sort out their problems, and i don't want to spend more money on htpc