Thats is why I try my hardest to avoid IAH like the plague!
Story time:
Trying to get from MSP to SAT. Missed the last direct flight and the only flight that could get me home that night was through IAH. If the flight was on time, I had 25 min to make the connection. Unfortunately had to gate check my bag, flying on the ERJ145. Made it to IAH a couple mins late and jump out to get the gate agent to ask her if she could call the other gate agent, let them know I would be running. Turned out, the other gate was on the total opposite side of IAH. (arrived A terminal, departing E terminal) The SAT gate agent at the E terminal said they'd wait. GREAT!! So like an idiot, I go sprinting through IAH at about 1045pm at night, on memorial day.
I get to the gate, and everyone is gone. I walk around, thinking to myself, "damn, almost made it." Out waddles a 300lb woman asking if I was jow blow commuter. I said I was and she replied, and I quote. "Oh, I took you off the list and pushed them 10 early."

"Well, thanks lady. Did the crew know there was another non-rev trying to get home on the last flight of the night." Well, that sent her size 49 panties into a twist and she started going off. I just smile, say "Happy Memorial Day from a Vet" and turn around to walk off. Right about then, the manager walked in, we had a nice chat and she apologized.
United gate agents, in every commute I've been apart of, are by far the worst..