I would be interested, Frank, in your comments about your SD picture via DTV vs. what you were getting from Comcast.
Bear in mind that DTV is connected to my Sammy DLP through the DVI port, while Comcast had to use the component connections. There's good news and not-so-good news:
First, DTV's SD channels are all much sharper (relatively speaking), with better colors and higher contrast than the same channels from Comcast. I'm sure they'd be superior even if I was using the component connections.
However, I'm so spoiled by the PQ of HDNet and Discovery HD Theater (as well as the local channels) that I don't watch SD if I can help it. For example, I was addicted to both Stargate series on SciFi, but after about a week of DTV's HD, I cancelled my Season Passes to both of them. I'll see those shows in all their glory if and when they're delivered in HD.
still watch timely SD shows such as The Daily Show. Like the other channels, The Comedy Channel is much more satisfying to watch now that I'm getting it from DTV (via DVI).