I was in the same situation. Their all-in-one modem/router is the most insufferable piece of equipment I've ever had to work with. Trying to do any kind of video chat using it was a nightmare with constant freezing and buffering issues even when standing right next to it.

Bought my own Surfboard and TP-Link router and installed DDWRT and have been free of most issues since then except one. I randomly lost internet connection once and tried everything that I could to get it back up and running. Finally got a technician out and he showed me that sometimes you have to keep the power on the surfboard and only unplug/replug the coaxial cable to the wall and then it will start working again. I had never seen an issue like that before in my life and I'm still trying to figure out why that fixed it.

I second this. With Comcast (business). No complaints coming up on the first year. Caveat: I don't need blinding speed to push code back and forth. Verizon DSL was fine, actually, when I used that.