I've had an HD Homerun for about a year now. The receivers in the HDHR aren't quite as sensitive as my television sets. Not aware of any scan issues - mine scans just fine. In fact it makes TV DXing quite easy. I'm splitting my VHF/UHF signal twice before it hits the HDHR and it still finds all the channels though. Curiously enough, it finds more sub-channels than my TV. For instance, WXXI's re-transmission of the radio station with the groovy graphics shows up on subchannel 200 or some such thing.

I built a MythBuntu box and it worked first time - I gather this is the exception rather than the rule. Hopefully you're also so lucky.