Actually Coastermania is not an ACE event. It's an enthusiast event sponsored by Cedar Point. Basically you just have to be a payed member of an enthusiast organization to attend and show your membership card (Coasterbuzz, ACE, etc.). With your membership card you can get 2 tickets (one for yourself and a buddy) both of which are discounted $10, and they provide a free lunch. There's a bunch of other stuff too like a big meeting with higher ups where you can ask questions and stuff. I went last year, it was a ton of fun. ERT was from 5am - 10am. Then you got to be in the park with the GP from 10am - 10pm. Then there was more ERT from 10pm - 1am. 21 hours total. It rocked.
I went to Coastermania and had a blast. It was in September this year rather than in June as usual due to ACE CoasterCon being at Cedar Point.
I'm not going to turn this into a trip report but if you ever get the chance you should go. I flew into Cleveland Friday and then drove to the park. It had been raining and was cool and windy so there were no crowds on Friday night. I got about 7 rides on Top Thrill Dragster on Friday night.
Saturday AM (6am) we had ERT on Top Thrill Dragster and Raptor which was awesome. Got to ride TTD with the lights turned out! 420 feet straight down into pitch back is something I won't soon forget.
The night ERT was Magnum and Millenium Force. Simply awesome rides with no trims to speak of on Magnum.