The Netgear CM500V will work just fine with Comcast including the voice service. The modem will only work with Comcast for voice. It is also certified by Comcast.
I installed one yesterday, used the online activation, and have had no issues with the CM500V working. Get one and save the $10.00 (soon to be $11.00) a month that Comcast charges.
The Comcast modem does include WIFI, the CM500V does not. If you need WIFI you will need an additional router to work with the CM500V. That is the configuration that I have, the CM500V connected to a Netgear Nighthawk R7000. Speeds are excellent and multiple devices are connected, wired and wireless, without issues.