I'd heavily advise ditching CI and hacking around with Kohana Version 3. Despite my misgivings it is super fast, super extensible and extremely powerful.

CI is just not updated enough IMO to form the stable base for an app.

As for taking it beyond blog content - I've created all sorts of complex sites; for example featured realtor website (property search, user management etc.) a wiki/"stackoverflow similar" site and am also working on a twitter "ticket" and marketing site (which is pretty complex). So it is suited to stuff like that.