In our experience, UA is thorough and efficient with their rules and procedures. After booking our flights, we fax the required documentation. About a week later, we call to confirm that the documentation was received and applied to the PNR.
Before arriving at the airport, our dog gets a long walk and is not fed. She gets another walk and trip to the pet relief area at JFK, EWR or wherever we are flying from. At check-in, we present the original authorization document, at which point we get a gate pass for our dog that allows her to go past security. After this, no one asks anything.
In 20+ trips, our 20 pound Boston Terrier has literally never made a sound, had an accident, gotten away from us or been aggressive in any way. She basically sleeps on my wife's lap the entire way, which is her "job." We fly up front so that no one needs to sit in our row (among other reasons of course). No one has ever objected to being near us (to our knowledge), if if they did I'd be more than happy to move around to accommodate.
I understand there are horror stories, though we've never seen one. As I have said elsewhere, poorly trained dogs and irresponsible dog owners should not be allowed on planes, ESA or no. People who bring dogs (or any animal) on a plane need to go above and beyond in terms of being respectful and accommodating. The person the OP came across obviously failed miserably in this regard, no ifs ands or buts.
As for us, we are fortunate to have never experienced even one drop of the vitriol some have expressed in this thread. Personally this leads me to think that the ESA "problem" is
way overblown. From the way some people carry on in this thread you'd think UA became a subsidiary of
Pet Airways. To be crystal clear, I'm
not saying dogs and their owners are angels 100% of the time. We've all read the stories, and there clearly are people who shouldn't be allowed to fly with their pets. But in my opinion that doesn't -- and shouldn't -- mean that "animals shouldn't be on planes."