If you don't like big crowds, this event probably isn't for you. My experience wasn't good, nor was it bad...it was certainly exhausting, though. That being said, I was working, which means that the 24 hour Disney day was not designed for my pleasure and comfort (nor should it have been).
I'd love to try one of these from a guest's point of view, because I heard very positive things from people that went to this event and the one that followed it. So I guess the moral of the story is less "don't go to this event" as much as it is remember to be respectful and courteous to the people bending over backwards to make it happen.
We came back at 10PM and weren't allowed in the park because it was at capacity. HUGE lines outside of Disney. We then came back at 3AM and got in, only to see all the good exclusive food was gone. The lines for rides were hours... I think I saw Space Mountain at a 4 hour wait or longer? I think we got to go on a few rides... Snow Whites Scary Adventure (over 30 minute wait) and a few other little kids type rides.
When we were in line for Snow White we saw TONS of local teenagers. One was doing some cocaine right in front of us (kid you not!). Really, the locals crowding the parks killed it for us (and I'm now a local at WDW).
The ONLY saving grace was that we go First Class both ways on our flight, and we were given extra magic and upgraded to a 1-Bed Suite at the Disneyland Hotel... but my guess is that the reason we got it was because the hotel was overbooked and we got in around 11PM... so they gave us a suite because nothing else was left. As nice as that was, the room was pretty much the farthest walk from any room at any on-propety hotel you could get.
Eventually I bought a "One More Disney Day" t-shirt online on eBay for $60 or something like that just to PROVE that I was there (since DisneyStore.com cancelled my order because they couldn't fulfill them all.... ahhhh!)
Overall, we hated it. When we saw the much lighter crowds at WDW we were very jealous. Now we live here in Florida so we may go to the one at WDW this year... although being allowed to dress up may make the party more packed.