I did install the new Xfinity “Internet/Voice” modem-router combination, offering 2.4 and 5 gig rates.
As usual, there were a few glitches in installing. The splitter end on my existing service had a longer needle than the new cords shipped, but after some difficulty I got it to screw on.
The device powered up fairly quickly. Use the exact router name and use full password pasted on the machine (not the pin). You have to go through "www.comcast.com/activate", which will connect even though the computer shows No Internet on the icon (and gives the name of the router pasted on the device). I found that if I didn’t completely turn off power to the old router, the computer would keep going back to it, disrupting activation. Also, the activation step did work when I logged on with my “Comcast.net” email username and password, but simply using the account and phone somehow didn’t work. (The second time around you use the names and pw you created, not the one taped on the box; you don't need this with Ethernet, which almost no one has now.) After “activation” the service prompts creation of a new name for the router and new password. Even with a long password, it rated by strength as average.” Finally, it accepted website access.
Kaspersky warns me that the connection may not be secure, but Windows 10 says it is secure.
After installation, the first restart of a HP Envy Windows 10 crashed immediately. I had left the printer and one camera connected. A push-button restart worked. The Windows event log says “user data access 84639e service not available”. The problem has not recurred. It may be something that fails “the first time” because of some kind of caching.