Nice. Seems very similar to other document based collaboration services, perhaps most notably these folks: http://www.collaborate.com/

Quip seems closed, no links to Google Drive or Box that I could see, and no way to share by PDF, but they include private links to hosted document storage. It's like the Asana walled garden[1] in that way, but Quip has a solid focus on documents not tasks.

Some strange UI artifacts on my iPhone 4s iOS7b4, text insertion didn't work; wonder if this is due to a proprietary attributed uitextview?

[1] http://asana.com/product

Curious: what does "/-/" it their robots.txt[1] do?

    User-agent: *
    Disallow: /-/
    Disallow: /account/