I am not a Triple Play customer, and I only have Internet service with Comcast, but I did sign up for the Home Security 300 service, and it seems to work well, if configured correctly.
Since the Home system adds a new network device (I believe that the Security & Control systems are different in terms of equipment), make sure that they understand what you have before ordering it.
I was able to get everything to work correctly with the Security 300 system with my own modem and router, but I know that there are others who have had issues with getting their Comcast-supplied modem/router unit to work the way they want after the Home system is installed. I think there are a few threads on the top of this topic that talks about it.