I'm now up and running with Comcast HD box (Motorola DCT5100) and my Tivo Series 2. In short, it is awesome. Set-up: Comcast box S-Video out to Tivo S-Video in. Then running Tivo S-Video out to Panasonic HDTV monitor. For live HD I run the component video out of Comcast box direct to Panasonic. Video: Recording HD programming from HBO, Showtime and others onto Tivo. My Panasonic HD monitor set to "zoom mode" displays correct 16:9 aspect ratio. Picture quality is outstanding, far superior to non-HD input picture quality but obviously not HD. Live component HD output to the TV is superior to Tivo recorded HD content. Audio: Comcast box is connected direct to my receiver so live programming is 5.1 Dolby Digital on HD channels (HBOHD, Showtime HD). Tivo audio is stereo output but the fidelity of the sound is superior to non-HD (Dolby 5.1) content. Results: In short, the combination of upgrading Comcast HD box and Tivo Series 2 is killer. Enjoy! Side note: If you are a Comcast HD customer, chances are you have the DCT 5100 from Motorola. Its worth hitting Motorola's Web site to get the documentation, Comcast installer was unaware of several features including digitial audio configuration set-up.