Here comes the bad news; pricing scheme seem to be surfaced with the launch plan and there will be three plans available to the users. Which are; Free (online only, all data public), Enjoy ($57/year, only works online) and Pro ($160/year, online and downloadable).
Sharing what you’ve created might not be problem for most of the users
but being not able to download and use your presentations offline will definitely hurt free users. Anyways, Prezi is a really innovative tool for creating slick presentations and definitely worth a try.
Update: It looks like its not the presentations that free users are not able to download, but the new “offline editor”. See comments for details.