There are many reasons why people stop flying an airline. In my view, it is because at the majority of the touchpoints that airline has with its customers, it fails. If United wants its brand to be successful over the long-term, one of the (many) things it needs to do is examine each of its customer touchpoints to make sure it is the best it can be. More control should be exerted over those areas out of UA's immediate control, including UX stations -- their actions reflect just as badly on the brand as a whole.
While I won't stop flying UA because of my poor experience this weekend, from the comments of those flying with me, they will no longer be sending their dollars to Chicago. The story that follows exemplifies this. Semi-venting, semi-demonstrating how a whole station can chip away at UA's marketshare.
Check-in at RDU: What a mess! The environment was loud and crowded. The staff was flustered and clearly enjoyed no aspect of their job. At several points one woman would come out from behind the counter and announce in a very paternalistic tone: "I have an announcement to make. If you are not checking bags, come up here and use the machines." (No one moved.) "I said (louder now) if you are not checking bags, please come use the machines." No one moved. She rolled her eyes and went back to her check-in location. The person behind me remarked to his family, "I'm never flying United again. This is incredible!"
The Premier/First line was staffed with the most inexperienced agents I have ever met in my years of flying UA. He took (literally) 20 minutes to check in the people with bags ahead of me. I used the EZ-Checkin machine and then had this conversation with him:
Me: Hi there! I heard this flight is oversold (handing him boarding pass for my second leg). Would you mind adding me to the VDB list?
Him: (taking the boarding pass and staring at it for a few seconds) You want an upgrade?
Me: No (chuckling), I would like to be added to the Volunteer Denied Boarding list.
Him: (grabs my other boarding pass) Why do you want to be on the DM list if you are already confirmed on the flight?
Me: Oh, not the DM list, the Volunteer Denied Boarding list; I want to volunteer for the flight because it is in an oversell.
Him: (pauses for a few moments) I don't know how to do that. Just a second.
He goes over and asks the woman mentioned earlier. She comes over explaining to him that I "want one of those free tickets" and shows him how to do it. They proceed to add me to the VDB list for the first leg of my flight (not oversold). Fuh-get about it. On to the next issue...
My friend is flying a UA-code/US-metal flight to ORD. I ask if they would add him to the standby list for the RDU-ORD nonstop since he is on a 016 ticket. The man, "Wait, is he flying US Airways or United?" (You can imagine the rest of the conversation. argh!!) He goes to ask the woman.
Her: "That's not possible. We don't do that."
Me: "Oh. But he's on a United ticket."
Her: "So? I said we don't do that."
Me: "That's strange. I've done it many times before. Is there maybe someone we could call that could help us figure out this situation?"
Her: (very aggresively) "Are you telling me I don't know how to do my job?!"
Me: "No, thank you for your help."
I immediately call the 1K line and get a
very helpful agent at the HNL center who agrees that yes, it is possible for him to standby for the non-stop and that the agent doesn't know what she is talking about. She offers to have her supervisor walk them through the process. I hand the cellphone to the gentleman ("Oh yes, hello. I don't know how to do it? You'll have to tell me.") After conferring again with the woman, who rolls her eyes at us, he proceeds to put my friend on the DM list
for the wrong flight -- a flight to IAD. AAAAAhhhh!!!

Well ,that will get us through security... and we rush off to the gate after being in the check-in area for nearly 1.5 hours.
Flights: Flight from IAD was oversold and delayed. OK, that happens. Staff (surprisingly 3 SD's working one flight!) was grumpy and (again) flustered. Lots of rolling eyes, lack of eye contact and none of the great service I have experienced in the past. Boarding was hectic (no control) and there was duplicate seat assignments galore and shouting at passengers to get in their seats, sit down, etc.
CONCLUSION: The level of poor, inept service I witnessed (and received) this weekend was scary; and IME atypical of United. I don't typically fly in/out of UX-only stations, but if RDU is any example, United had better come down hard on UX to set higher standards for their staff; sooner or later, the tail will start wagging the dog.