I know this is disputable, but if Comcast gained serious share which I'm assuming is the eventual goal, I think it'd be bad for broadcast TV, to (pay tv) Comcast's gain, just so Comcast has some additional content in their vault to play with.
NBC and the O&O stations would be marginalized much quicker than otherwise. First with recurring contract disputes with DirecTV and Dish Network and Verizon, as Comcast hikes the retransmission rates, cited by programming increase because of sports rights (NFL). I'm thinking Comcast NBC will outpay the other networks for sports access. Dish would be forced to drop stations during renewals, cutting exposure at times. Local newscasts in some markets like Philly NBC 10 could follow CN8 news, CBS Detroit news. Overall reducation.
Leno and Today would make it to the On Demand system, and overexposed, but other units like the network news division and Telemundo would see cost cutting and noticeable quality reductions and/or divestiture, with those channels following a path like CW, MyNetwork and Pax/ion.
The cable channels would have a few new quality shows (mainly shows that would otherwise have gone to NBC) repeated multiple times, but the channels would be overall poorly handled with reruns of a couple shows, blocking schedules with a huge on screen logo (think Lifetime TV) covering 1/8 of the screen, making even the HD channels unwatchable. Atleast with the broadcast network model, you'd have affiliates that wouldn't put up with that.