This was the fastest beta invite confirmation ever. Unfortunately, Digger‘s Terms of Service do not allow any sort of disclosure about features or results from it. This is very different from Powerset which has been going out of its way to get beta subscribers (even unconfirmed ones) to know what they are doing. Digger does not even seem to have a blog, which contradicts the rules for a web2.0 company.
I hope that the difference is that Digger is in the earlier stage than Powerset. If they are not, then Powerset may win this competition just on marketing alone.
So, the only thing I can say about Digger is that my previous idea about them wanting to be really sticky seems to be right on the money. Until the Terms of Service change, you will have to get a beta account yourself to see any more. Or you could apply for a job there.