I'm definitely excited about the extra day of con. I only usually end up hanging around conspace and loitering in cosplay, but that's one more day to do so! W00t.
Also, I am very excited to just generally meet new people, reunite with friends I never get to see throughout the year, and peruse the DH/AA. The four days may actually give me a chance to go watch some new anime in the viewing rooms. I never can make time for it, and this might just be my opportunity. Also, the Cosplay Competition (for the same reason). I never can justify the amount of time it would take to enter the CosComp, but with four days, if I get a legit cosplay together, I may have to go for it.