The problem I have with ZoS' maintenance is it seems like there's a complete lack of consideration on ZoS' part. Flame me if you want, I really don't mind.
Some sort of ETA should be provided. It's called customer service. Yes people may get angry if it is longer than expected, but tough... It's an estimate.
Real customer service involves keeping people informed. You provide an estimate, and if your estimate is not going to be met, you update your customers.
Here is an example of how this would work:
Servers are coming down at 6am EST. We expect services to be online at 8am EST.
At 7:30 EST they realize things are not going as fast as they planned and they post something like the following:
Unfortunately things aren't going exactly as we planned. We're encountering unforeseen problems and we expect the return of services to be delayed an additional hour. The new ETA for the return of services is now 9am EST.
Now seriously, how can anyone complain about that legitimately? That is very considerate and exceptional customer service.