Last week, I added Internet service (and telephone as soon as the porting process completes). I picked up a CGM4331COM gateway at the Comcast store, installed and activated it with no issues. My TV service uses a TiVo box, no Comcast equipment there.
Shortly after I got everything installed and configured, I noticed that the gateway was hot to the touch. It sits on a shelf, with no restrictions to airflow. Internet searches haven't turned up anything recent about heating problems. Ambient air temperature is in the mid 70's, the top of the Gateway is 120 F. as measured by my IR thermometer.