I think there is one limitation or bug in SHARES that works out to be slightly positive - because award tickets retain the FF number of the account that issued them, the system keeps the status of the issuer on the reservation. So when giving tickets to family members, they may select E+ without having the Elite member traveling with them in the same PNR. There also isn't the automated sweep that removes them from E+ if the computer detects they don't have status/payment. Please correct me if I'm wrong, but I believe PMUA would have those members sit in E-. I believe it works for baggage allowances as well.

That being said, it seems clear the United system is much easier to train and use for everyday tasks. I'm still surprised they decided to take such a large step backwards.