I'll take a shot at it:)
I used the S-Video input on the Hipix to upscale the output of my TIVO to see if I could improve the PQ from the TIVO.
The Hipix is feeding 1080i to my Mits HDTV.
I found NO improvement in the PQ. The Hipix acted like a simple passthrough.
The Line Doubler in my Mits does a better job.
What the other folks are talking about is using a capture card and the Dscaler program for improving PQ.
I tried that too and there was a definite improvement. However, the picture from Dscaler jittered too much.
I am back to just using the internal line doubler in my Mits.