I could type out a novel on the horrible experiences I have had with United Airlines, but I will only talk about my most recent trip. I flew from PHX to LAS. I opted to go a longer route since First Class was going to only cost me $90. I flew from PHX to LAX then LAX to LAS.
First off, the service at PHX that United has is a horrible excuse of help. They are rude, mean, and disrespectful. Once on the plane, I had such great service from the flight attendants in first class (usually its horrible, but i'm assuming it was great due to being in first class). Once I landed in LA, our flight to Vegas was delayed by an hour and a half due to another aircraft having to drop passengers off before our plane could park and let us board...so here we are waiting an hour and half in Gate 80 for our plane to park and let us board when the entire time (and even after we left) Gate 81 had absolutely nothing topping it from being used. Instead United made us wait. This happened in Denver with a previous flight as well. They couldn't find a pilot....how?
Anyway, I have far too many vouchers from United Airlines due to their horrible treatment of passengers so I fly them here and there just to use them. I always and forever will be an American Airlines person due to their service and support.
The only shout outs I have are to the the customer service reps I spoke to on the phone who waived a change of flight fee ($200) twice and also to the really great staff who were just as upset to be delayed when we were. HIGHLY recommend other airlines.