Well this is awkward... I'd be interested to hear what the actual cause for the delay is. In my opinion it has to be something completely out of the blue and unavoidable for 20 hours notice to be justified. Somehow though, knowing this project, I doubt it somewhat :/
It's all well and good saying tickets will be revalidated, but what about the people who will have already made hotel and transport booking, etc which cannot be altered? For a lot of people these can be just as much, if not more, than their park entry, and for lots of families a trip to Alton Towers is a once a year treat. At the very least I feel AT could have offered Smiler priority passes when it eventually opens, and possibly a heavily discounted hotel stay as a good will gesture.
The Smiler - Alton's biggest flop since Splash Landings opening