US is definitely not the worst. Ever had to deal with CO when flights are delayed? Cant even get through to talk to someone on the phone. Routinely 20-45 minute waits. Once they had a mechanical delay on my 10p flight to GRU. Started out as 2 hr, then 4 hr (eventually cancelled). I would have missed my connection and screwed over the start of my vacation if it were up to CO. I couldnt get through at all to CO to re-route. \
Had to call UA to fix.