>The combo units my local Comcast affiliate leases out are a mess of problems, and I know multiple people that have gotten fed up with support never fixing the issue and just accept the frequent problems.
TW->Spectrum where I live seems to have a pretty common practice of simply taking the modem from customer 1 complaining about internet dropout/etc and giving it to customer 2 complaining about internet dropouts.
Besides the bad router hardware, in my experience with the cable companies, a large part of the problem has been signal issues going through old cables, splitters, etc. The one advantage to owning your own modem is you can select one that gives you good signal quality metrics and error reporting.
Which brings me to what I view as the fundamental issue here. The cable companies frankly don't give a crap about service quality. They _CAN_ monitor signal strength, dropped packets, signal loss, etc from their end. With that they could act proactively, like "Hey this customer's modem won't lock on 1/2 of our frequencies lets call them and send a tech to fix it".
But they don't, and really that tells me everything I need to know about those companies.