The picture may be a little better when using the HDMI output. When using the component, it's at least as good. The 520 has VGA output, right? I think that's what I was using when I had mine. Quality wise it's not a downgrade if that's a concern.
My HDMI port has quit working which is a common problem with the 250's. DirecTv has replaced it 3 times. The third time the HDMI port was working fine for 6 months or so, then went a little crazy after I upgraded the drive to a 400gb. So I've been using the component outputs and I'm happy with the picture.
If you haven't done so, you should check out the tivo community forum. They have lots of good and bad points about the 250. I can't live without Tivo, so the good points far out weigh the negatives.
http://www.tivocommunity.com/