>> Office documents don't seem to be a make-or-break feature for social, and Google Docs has had very limited success competing with Microsoft Office.

If any app being social means being popular among general web users than yes Google Docs / Office document is not make-or-break feature for social. But when you use Google docs within an organization for team collaboration there is no better tool than this I've found so far. I doubt whether they are working on Google Docs desktop or not but I think that will be a one on one competition to MS Office.

>> (in fact, my favorite Google office productivity product, EtherPad, was killed in favor of Wave)

Etherpad was simple tool. Yes, we can't run it on etherpad.com, does it means they killed it ? I don't think Google killed it, they opensourced it. There are plenty of other hosted options available and are linked at the same domain http://etherpad.com. Why don't use them, they run Etherpad as well.