$39/mo is much more than what it costs to self-host Confluence, which for all its flaws at least leaves you in control of your data and is super extensible.
Improve the data portability story and it'd be a lot more attractive.
Additionally the actual docs and demo site are not loading in time from Australia. The `main.{digest}.js` file is reliably giving me a 15s download time (not TTFB, oddly) (http://i.imgur.com/ay6le8H.png), which causes the entire page to be blank. I have like a 300MS RTT to the server. Get a CDN and use it effectively.