The industry standard is .PDF. As long as you can get to .PDF, all is good. All modern screenwriting software supports the Fountain syntax, except Final Draft. Final Draft is the dinosaur of the industry, and they are dying. One man shops are making far superior software at a lower price and that are far less buggy.
One you get into production, Final Draft might be needed, but many places aren't updated their overpriced licenses.
The top "traditional" software packages for screenwriting now are either Fade In Pro ($50) or WriterDuet (free/$99 one time license for all the extras). Both support Fountain.
http://www.fadeinpro.com/page.pl?content=comparison
If you're only writing in Fountain and then to PDF, Highland and Slugline are the other options. They are both under $30.
I also like afterwriting.com. Bascially it's Highland in a browser that can sync to Google Docs and Dropbox for free.
The great things about Fountain is that you can just use any text editor you want and then import into a Fountain compatible package and that it's very readable.
The only "key feature" they have is that everyone in Hollywood uses FD. They say so themselves on their website! The "Key features" screen does not list any actual feature, it's just a list of variations on the concept that "everyone in Hollywood uses FD". In that sense, the main challenge is clearly political rather than technological.
Final Draft is the industry standard at the moment, and it has been for 20-odd years. To disrupt it, you could explore certain channels: dedicated websites and communities for writers; USC, NYU, and other film schools; or get studios and and agencies to accept it, which is ultimately where you need to win approval to get adopted as a standard. In any of these scenarios you'd probably need Final Draft import/export compatibility to get started and minimize switching costs.