One of the irritating things about united.com had been the way it failed to handle seats for itineraries upgraded during the same login session. In particular, if you upgraded a flight and then tried to select seats via "my itineraries", it showed the original cabin seat map and class of service, not the upgraded cabin. In order to select upgrade seats, one needed to either wait for the session to time out or manually log out and back in.

They seem to have actually fixed this recently. When I upgraded some tickets I bought last night, the screen shown after upgrading had an option (a bit hidden toward the bottom) for "seats", which actually put me in the cabins to which I had upgraded.

Now if they'd only stop pretending that upgrade inventory is some kind of state secret...