I have a bunch of ATI AIW's ... mostly agp but also an x600 and x1900 in my sons rig. I don't think he is using it for hdtv tho ... he has an hd pvr and lcd tv now ... the aiw is just an input to them i think. He has HD via cable so no experience with antennas.
My AIW tuner experience's were pretty good so hopefully your HD one is too
