Their official blog is a tumblr. This does not bode well for their status as Serious Business. (I like tumblr. Mostly. But it's not designed for serious discussion, or even serious long posts.)

It lets you read DRM-free epubs and apparently blog posts & similar on an iPad (well, that's what the blog says; the site's picture shows a laptop), without distractions. I suspect a storage app combined with a "readability" plugin, and a bit of social options.

I've signed up for beta. The app's not actually available yet. If it's iThing only, I'll let people know.