Go on day at least...heck I;m going to get to the parks when they open head on a few rides then move to the Expo walk around have some fun and see the Disney Movies presentation and then Lion King after that head back to the parks for some nighttime fun...worth the 40 bucks? Heck yes
Getting my first Duffy bear and seeing WoC for the first time.
I went last year, and the announcements were a small part of it. The Disney Parks and Resorts area was especially fascinating. And I also really enjoyed the Mr. Lincoln and Science of Imagineering presentations. It was really fun, and I highly suggest you try it out this year!
I think it's going to be a mixed bag. Imagineering (Parks & Resorts) pretty much pulled out all the stops for the first Expo, and pretty much held it together. While they will be showing the new WDW Fantasyland, most of the rest of their exhibit will probably be a rehash of that first show.
So as far as their part of the Expo, I don't know how much of a real draw they will provide this year. Of course, any opportunity to chat with an Imagineer is probably well worth it.
Outside of the Parks & Resorts exhibit, there will be the assorted other Disney business units. The studio and Pixar elements will still be a draw. However, compared to the park and studio related aspects, those there for the likes of ABC, ESPN, Disney Channel, etc. may still be as light as the last Expo. Unsure how much enthusiasm thy may show over their last efforts.