i have had Comcast for years and have been happy so far. their interwebz has been dependable and the few times I've had them to my house they did a good job.
their basic cable is way over priced but all TV is way over priced to me and that's why i cut that and have a digital antenna for TV.
but for $40 a month (what i pay) for internet only, it's a good dependable connection that i have had minimal problems within the last 10 years or so. i do feel the interwebz i'm getting for $40 a month could be a little faster but........
i ditched their modem and got this:
after i installed the Motorola modem/router there was a noticeable difference in page load time and the range on the WiFi covers my entire property. (4 city lots) without a problem.
i also had no problem returning the POS Comcast modem. i just called them and they told me where to drop it off and did not charge me past the day of it's return. also, the aftermarket modem auto detected through Comcast so the install was simple.
i rented the POS Comcast modem for years. wish i would have went with the unit i ended up purchasing years ago.
either way, i'm happy because they have been very reliable thorough the years and i have had minimal problems.
my 2cents FWIW