OK, I humbly bow to the superior knowledge of doppler.
First of all, the installer guy came around 11, and no, it was not a TWC badged employee. AND this was his first install. BUT he had an HD-DVR, so I promptly snatched it from his hands and installed it myself. Piece o' cake.
Now, in deference to doppler, my TV does not receive any signal from the S-video output. I even set the output on the HD box to 480i only and unplugged the component cables. Nothing.
But after messing around for awhile, I have stumbled upon a way to use my TV's superior stretch mode instead of the cable box's. What I did was set the Aspect Ratio as follows:
TV Type = Standard (4:3)
Picture Settings = Letterbox 16:9
Now, keep in mind I have a 16:9 widescreen TV.
By doing this rather odd setup, on the SD channels I get all my TV's aspect ratio modes, including the 4:3 stretch mode, behaving as if I'm getting an SD signal -- i.e., they all work! Even though the signal is 480p (according to my TV). Popping over to the HD channels (250 and 280 are on this morning), they look fine -- receiving a 1080i image and displaying them in all their HD glory. I even switched to the OTA WJZY feed just to make sure my eyes weren't deceiving me. But sure enough, it looks right.
Now, YMMV, depending on how your particular set handles the signals. But for my CRT RPTV set (Hitachi 65XWX20B), this seems to work.
BTW, I have ALL Output Formats selected (480i, 480p, 720p, 1080i), and my TV indicates it receives them in the latter 3 formats, depending on the channel. All SD channels must be upconverted by the HD box to 480p; but WSOC and WCCB show up as 720p, and the other HD channels show up as 1080i. So I guess by selecting all formats the box is passing through the signal as natively as it can.
I'll check back in after tonight with my thoughts on SD quality, as well as cable box vs. OTA HD signal comparisons. On first blush, the SD quality looks about the same as my previous SA8000 (non-HD) DVR, which is to say crappy, but keep in mind I'm sitting 10 feet away from a 65" television, so it's not gonna look very good to begin with.