Digital converter quality question

I've bought a couple DTV converter boxes from Goodwill. Some new. Picked up a Channel Master w/remote for $12. that I hooked up to my old Philips DVD recorder via S-Vid input. So can record OTA digital broadcasts onto re-recordable DVD discs.

Though recorded as 480i SD on DVD, the output is upconverted to 1080i HD via HDMI to my LCD HDTV when played back. Actually, a surprisingly high quality picture.