I really think Overview is one of the least useful things in G3 (I rarely go to it). It could be fantastically useful, perhaps integrating something like OS X Dashboard, but it keeps getting more "designed" (i.e. little functional change, but some UX changes). As drag mentioned, Zeitgeist journal was supposed to make an appearance (there's still an extension for it though, IIRC ). Now, instead of having a really smart overview search, we're given micro-apps like Documents, or the various Media ones that've been mocked up. So it seems like Overview, while having the ability to consume arbitrary asynchronous providers, will increasingly expect that ability to go unused in favor of going to these micro-apps.
It really seems like a bit of a disorganized mess.
That said, it is still better than Gnome 2, IMHO.