Self-service check-in as a non-UA *Gold is what I dislike, for it means no E+ unless later getting manual intervention by a UA agent/RCC lounge agent elsewhere, which, in turn, means hoping that decent seats are still left at that point.

It's rather disappointing that UA's systems don't recognize the value of non-UA *Golds, particularly those non-UA *Golds who fly UA more than enough to be UA 2P, 1P or 1K elites if they were to choose to use UA's program. Fortunately, UA's agents are generally more than willing to put me into E+. (The problem is when checking in at a station where UA doesn't have flights getting E+ isn't an option until arrival at an airport from which UA departs.)

I have noticed that on my Econ+ flights it's not been too hard for people in the forward rows of Economy to jump into Economy Plus on the longer-haul flights.