It breaks apart; it's choppy. No static, but virtually unusable as a phone conversation. It's intermittent, though, and I don't see what could trigger it (which would point to a Comcast pipe problem). Next time it happens, I want to test if the same phone conversation is better if I switch to a handset closer to the base unit.
I find it interesting that there's a flyer in the box for the new Panasonic unit for a Panasonic range extender. "Double the range of your Panasonic DECT cordless phone, so you can be sure to get your calls anywhere in the home." The wifi range extender I installed did help, but it's not perfect (which, again, might point to the Comcast pipe as the culprit).