In addition to upgrades post check-in being handled more elegantly by CO IT, I believe the same applies to other changes during OLCI and after check-in

For example, I recently changed seats during OLCI and my UA iphone app mobile BP showed the new seat, but both the Iphone app Itin and the united.com My Itins continued to show the old seat assignment... IIRC they are driven by a separate system that does not synch with the one used at the airport

Also, it's been mentioned a few times, but Elite Access privileges for awards redeemed from elite accounts (even if the pax isn't elite) is a nice benefit, IMO