I discovered that we did receive the "new HD channels letter" in Elk Grove after all. My neighbor, another Comcast customer, told me he got it last week and then my sigificant other finally told me we received one a week ago, but she threw it away without reading it closely or showing it to me.
On another note, Comcast Sacramento's usually inferior, standard definition digital channels (2-99) looked pretty good last night -- after weeks of medicore picture quality. Since the ADS conversion on all channels became active a few weeks ago (if you have a replacement Motorola DCT-64xx series cable box or DVR encoded to receive this), the picture quality on most digital SD channels has been compromised by heavy MPEG compression.
In our Elk Grove area, we typically see SD characterized by fuzzy pictures, heavy MPEG pixelization, clayface, color banding and motion problems, distracting compression artifacts around type and graphics, visible electronic noise, and reduced dynamic range in grayscale and color scenes, even with a high-quality plasma HD display! When sitting eight- to ten-feet away from 40- or 50-inch displays, you easily can see visible MPEG-2 tiling on most Comcast digital SD channels. Worse (in Elk Grove at least), the SD picture quality seems to vary from day-to-day and even hour-to-hour as neighbors come online near the end of each day.
Last evening's change for the better was sudden, inexplicable, and similar to a short-term inprovement I've noticed twice before, so, I am not yet even "cautiously optomistic" that a permanent improvement is in the offing. However, since I am a frequent critic of Comcast Sacramento's less-than-professional cable TV services, it is only fair to note such improvements.