I personally like EUA. No more midnight calls to the hotline. EUA might have some issues needed to be resolved, but it beats staying up until midnight and waits another 20 minutes until it's your turn to talk to the agent.

Check the Delta board and you will read the heat about the LU non-upgradeable fare. I know quite a few people switched from Delta to CO for this reason. People on CO board complain that HoKeY fare, but at least you can pay extra to buy the upgrade with miles. Delta's L/U is absolutely non-upgradeable.