From the wired side, since the AP's bandwitdh is separate from the paying customer's, the later really has no complaint to make. Taken to the extreme, yeah, all those APs may end up adding to the load on the coax segment and creating congestion. But somehow I doubt this is a huge issue.
One the Wi-Fi side, it all depends on how much capacity on the paying customer's Wi-Fi SSID is reduced by the presence of the Xfinity SSID. I think Comcast should have spun this totally differently. "Guests coming home ?, go to your Comcast web site and enable Xfinity, and they can sign in with their credentials to your Wi-Fi, and won't slow you down or consume your monthly usage limits". This would have been seen as a true service given to consumers instead of being seen as Comcast "stealing" consumer's bandwidth without their consent to serve others. (which is what the perception appears to be) As far as the electricity issue, I have to assume that any alleged additional power consumption would be very minimal compared to a router that has single SSID. The principle may be worth fighting for, but the amounts are not.