A year and a half ago the product was in early alpha ;) In that time we've revisited and redone a lot of components that have unfortunately kept us in beta longer than we would've liked (we've gotten rid of the virtual drive, rewritten some of our syncing algorithms, and are working on another major re-factor based on user feedback now).

Hard stuff is hard. When you're working on something deep and new, as I believe the AeroFS guys are, you can't necessarily know how long it will take.