All the data is stored in the cloud and synchronized between multiple devices, with version histories of everything you write.
As we flesh out the software, we'll also be building realtime collaboration, writing groups, etc... So in the long run, philosophically, it's more of a service than a single piece of software.
We're a brand-new startup, and we're iterating the product fast. It's better for the customers, and for us, if we offer frequent updates to all subscribers, rather than releasing one big new version per year, and hoping our users upgrade.