Structured datasets are hard, and the hardest part is finding one that updates as time passes and new data is available - how are y'all handling that?
We're working on an API that will allow sellers to programmatically refresh their dataset to keep it up-to-date with the source. We're also working on a search and filtering system that ranks datasets based on when they were last updated.
I'd recommend you find, package, and sell other datasets that exist out there (Freebase, etc.).
I disagree with the registration requirement - if I want to be updated, make that a opt-in box - but I acknowledge that it's a justifiable product decision.