Thanks everyone for your responses! I'm sorry that I have been absent for so long. I started planning and packing for my move on the day when I posted my question above. I moved to NH on April 5th, and have been without TV or Internet since then because I have been so busy.
I finally got my TV and audio system setup Monday night, and went to the Comcast walk-in store today during my lunch break. Picking up the cable cards was painless. After a brief chat several days ago on Comcast's website regarding their services, I decided to buy my own modem rather than pay $10/month for their crappy modem/router combination. I already have an excellent router, and a brand new Motorola modem was $69.99 on Amazon with free prime shipping... so it will pay for itself in 7 months. In Florida, I lived in "Lightning Alley"... where life expectancy for a modem was less than a year... and BHN only charged $4/month to rent one... so it made sense to rent. Now that I'm living in the Northeastern US... I will gladly pay $70 for a modem vs. paying $10/month for one from Comcast.
So, I just picked up my cable cards today at lunch. When I got home... after dinner... I plugged in the modem. It connected with no problems. According to Speedtest.net, I get 86Mbps down, and 6Mbps up. That's better than the 75/5 that they advertise, so I'm happy. All of my signals are well within spec... downstream ranges from -7.7 to -8.6, and upstream is at 46.0. I may be able to improve those further. Currently, I have a -12dB tap. The other side of the tap is less than -1dB... which feeds a -3.5db 2-way splitter for the tuners. I could replace those with a balanced -5.5dB 3-way splitter. I need to do some testing on my tuner signals before I make that call. Ideally, I'd like to see the downstream power closer to 0, and the upstream power closer to 40dB on the modem. That will give me plenty of room for fluctuations due to weather conditions.
I'm in the process of detecting channels and downloading new guide info right now. I will post back with more info regarding signals for my tuners later.
So far, the experience has been painless. The only surprise (for me) was when the Comcast rep at the walk-in store told me that she didn't even know what a Tuning Adapter/Resolver was, nor did she know what SDV/Switched Digital Video is!!!
At first, I thought that she must be a complete idiot. Then, while I waited for her to put info into her computer, I Googled "Comcast tuning adapter"...
From what I saw in my search results... Comcast doesn't use SDV. I guess that explains what I've read about Comcast's picture quality. They must compress their signals a LOT in order to avoid using SDV.
So... that brings me to the point of my original question:
What I really wanted to know was what kind of Picture Quality (PQ) I should expect from Comcast?
On BHN, the PQ of the local broadcast channels was identical on OTA and cable tuners.
What's your opinion on Comcast PQ?
I saw the thread about Comcast using H.264 and DRM... and it doesn't work on XBox360??? Is there any fix for that???
OK... so I'm off to get my TV channels setup in Win7 Media Center. I'll post back with my results. I appreciate responses to the two questions above about Comcast PQ and H.264+DRM on XBox360.