There was another review which pretty much echoes my experience except that my modem started to fail just after the three-month mark. It's a real shame because in the 10+ years I've purchased my own modems (just two prior to this one) I've never had one fail before, let alone fail in just three months of use.
Everything worked exactly as expected from when I received it on January 18th, 2020. It was only a few days ago when, out of nowhere, the modem just stopped working as intended. In summary, it could download content, but uploading became very inconsistent, thus making video conferencing all but impossible. On top of that, the overall connection became spotty at best, working for a few hours before completely staying dead for another few hours.
Given the shelter-in-place order my state is in right now, not being able to effectively work from home without a reliable internet connection was completely unacceptable.
Of course I blamed Comcast first.
A technician came to my home yesterday (very helpful, knowledgeable, and a DIY PC builder like myself) to inspect the hard line from the street, the line from the box on the side of my house to where it directly connects to the modem, and the modem itself. They upgrading some cabling in the box, but other than that the signal strength for them was strong and healthy. After several repeated attempts to get the modem to work, the conclusion was that the modem itself was at fault. After weighing the options and examining the evidence, I decided to accept their XB6 modem as a replacement.
I'm REALLY disappointed at my Netgear CM1200 modem crapping out, and so early into its life. Though I haven't rented a modem in a long time, I'd rather do that right now than risk spending another $200 on a Netgear product that might die within a quarter.