Ability to organize my ebooks. I don't care if they call it folders/directories or bookshelves or bins or whatever. The 'collections' work, sorta but without a way of sorting and sub collections they are hamstrung and not all that valuable. I'd especially like to see advantage taken of the 3G to help categorize ebooks since the meta data in many is the sh*tz.
I'd pay for a really good organizing app for sure.