I made a reservation to get a new modem last year. When I got to the store there were more than 2 dozen people waiting, some had been waiting for quite a while. I got bumped to the front of the line when I walked in. If looks could kill I'd have never gotten out of the store alive. At least 1 of those waiting went up to CSR to complain very loudly.
I'll never go to any Charter/Spectrum store without a reservation.