Personally I haven't had this problem. In fact, every few months they actually increase my plan's advertised max download speed. I wouldn't say the actual download speed is as close as what they say but pretty close.
Of course the upload continues to be terrible
I use my own modem and router now but this was the case when I "rented" from them as well.
This! 2 weeks ago my internet started dropping for 1-2 minutes at a time, 3-5 times per day. The modem status page tells the tale, millions of uncorrectable errors, SNR below spec on several channels, and the event log shows all the disconnects. Neither their chatbot, nor the first level human support however will entertain any possibility except it being an issue with "the website you are using" or "your TV" or "your computer". Took maybe 30 minutes of BS until they offer to send a tech, but I have to pay if the tech concludes the issue is on my end. I eventually lost my temper and just told them AT&T is going round my neighborhood right now running fiber offering to buy everyone out of their Comcast contracts and that they have 2 choices, either they come out to fix the issue or they come out to disconnect and clean up my cable drop - their call. Suddenly a tech was available, the next day, guaranteed free of charge. The tech arrives, plugs in his test modem, says "yeah...that's not related to your equipment" after 5 seconds, shows me a huge signal drop in several frequency ranges and is actually surprised that the internet is even usable at all. Unfortunately the issue is further upstream than "our" utility pole, but he ran a new cable drop just in case and cleaned up on the pole before filing that ticket.
It makes you wonder how many people are limping along with half-broken internet just because they don't know how to debug this and force their way through Comcast's support wall and there not being a competitor they can threaten to switch to.
At this point, whether I’m speaking to my ISP or Amazon, I tend to demand a supervisor immediately, and in many cases, a supervisor’s supervisor. I refuse to speak to someone whose entire job is to _prevent_ me from receiving effective support.
Of course the upload continues to be terrible
I use my own modem and router now but this was the case when I "rented" from them as well.