Tuning in Digital Cable (QAM) channels on TivoHD

Just got a TivoHD. I know that Comcast in my area puts out digital channels (using what is called QAM) and the Tivo supposedly could tune them in, but it wasn't at all clear to me how to get the Tivo to do that. Here's how.

• Go to TiVo Central, Messages and Settings, Settings, Channels, Channel Scan.
• Select "Scan for channels" and settle in for 10-15 minutes. In my case it was half way through before it even found any channels, but it ended up finding 200+!
• After it was done, I went back to Live TV and looked for my new channels, but couldn't find any but the ones I had before. Hmmm...
• Ah, select "Guide" and then press Enter to bring up the Guide Options. (Update: see end of post for what is probably a better approach than this.
  
• For "Channels" select "All"
• Now you should see a bunch of new digital channels (they'll look like "12-1") in the Guide as well as when you surf through the channels.

Having figured that out, I still have to say I'm a little disappointed:

• There is no show information for any of the digital channels.
• Most (90%+!) of the digital channels seem to have no actual content, I just see a grey screen.

Now I suspect neither of those is Tivo's fault, I suspect it's Comcast's.

I'm not sure if there is anyway to have Tivo ignore the channels with no content. Plan to keep poking around with that.

Update: If you go toTiVo Central, Messages and Settings, Settings, Channels, Channel List you can mark which digital channels you receive. Once you have done that, under the Guide Options, leave Channel at "Chans You Receive" and then you will just see the channels you get.