said by DocL :
I'd like to avoid using the IR cables. I did use them for several months last year, and found their performance disappointing at best in terms of changing the channel to the expected channel; they had a strong preference for tuning to the low single digits (I had a long talk with a Tivo tech about this during the summer; they sent me a replacement serial cable, and I was suddenly in channel tuning heaven).
I hadn't known that Comcast doesn't support the serial Tivo connector; that's dismaying, since the IR connector functions so poorly.
Get a DVR box. Problem solved.