Long story short, this modem will reset itself and require me to not only become aware that it's once again broadcasting the "xfinitywifi" hotspot, but to also redownload the xfinity app, configure the app with my information and try to remember where they buried the setting to disable this "feature". After disabling it somehow takes up to 24 hours to actually happen....
In most areas, the modem rental is $14/month. Adding unlimited is $11/month, for a total of $25/month.
In most areas, adding unlimited to your own modem is $30/month.
Thus, in most areas, switching to your own modem with unlimited costs $5/month more.
Indeed they were surprised I DIDN'T want a Comcast modem, instead opting for a Surfboard/PFsense combo setup