Jon,
According to a KWC representative I spoke with a while back, their database is updated "every 10 days". However, I suspect the data to be a little older than that. He recommended I use the "KWC Live" version, which is still in beta, but pulls realtime data (which also makes it slower than the db version)
So far, I have seen anyhwere from 20-50% of the "Average CPC" reports in KWC. Keep in mind that their estimates represent what the advertisers pay on average to Google - not what you will get paid eventually from Adsense. Google eats their share of that CPC too :xomunch: