The big problem with Docs is that it isn't really secure. If it's gonna be cloud computing all the way, then I as a user have to be sure that my docs aren't gonna be intercepted by a MITM or a cross-site scripting flaw. I use the Writely part of it at work as a quick repository for info I need quickly, but the company firewall recently blocked it and I when I asked why I was given links to posts from security researchers exposing big time cross site scripting flaws with it that made me rethink how I use it.
Other than that, OO all the way for me!