These scores are from a sample of mail to a few beta testers.  They should not be taken as an overall rating of a domain.  We will need many more users to get better statistical averages.  Even with only this small sample, it is clear there are huge differences between different domains.

Another factor affecting these ratings is the use of default authentication records for many senders.  These default records include large IP blocks in the sender's allocation from a Regional Registry.  Many senders can improve their ratings by simply publishing a list of their authorized transmitters, excluding the "zombies" in these large blocks.  The spam from, for example, would have been zero if we had rejected what appears to be a zombie in their netrange.  Anything we can reject does not count against a sender's reputation.

Statistical details:

Total connection requests   16,581
   "     "        rejects   10,883

     Connection rejects included 154 forgeries of the HELO name, and the rest
     from the CBL IP blacklist.

Total messages processed     5,988
             whitelisted       799
            rated as ham     2,466
           rated as spam     1,060

In the "whitelisted" category, 3% were spam.  Most of these senders responded quickly to spam reports.  Only one had to be downgraded.
In the "ham" category, about half of the messages are spam.  Ham is defined as any message with a SpamAssassin score less than 5.
The challenge now is to increase the number of whitelisted senders until we can safely ignore anything that isn't whitelisted.