I've had slow internet speed for 2 years +. I've called Xfinity numerous times, with the same result each time... they waste my time each time doing the same troubleshooting steps that have already shown that the problems are due to Xfinity equipment itself.
They replaced my modem AGAIN about 2 weeks ago, and I upgraded my plan to the 1G plan. Speed tests show that I never get close to this speed, with top speeds in the low 700's mbps,. and usually around 600 mbps.
I live alone, and only have 3 devices that use internet... TV, Macbook Pro, iPhone. The TV cannot stream Amazon Prime even though it's hardwired to the modem.
But I just found a major reason that my wi-fi is so slow. I hard wired my computer to the Xfinity brand (new) modem and my speed test jumped to over 900 mbps from under 600.
So I'm writing this for all the other users who are frustrated by slow internet speeds... to let you know that if you hard wire your computer to their modem, performing speed tests before and after, you may also discover that it's Xifinty equipment that is solely to blame.
You do realize that WiFi will never get the same speed as being hard wired, in fact the farther your device is from the router the slower the WiFi will be, if your getting 600 Mbs on WiFi count your blessings