I've just separated all my mail from mid May til now into spam and ham for the Mother Of All Bayes Training. In case you wanted to know...
Ham: 25 megs 4201 messages
Spam: 201 megs 6553 messages
Rules based SpamAssassin missed about 1300 messages in that period.
If that sounds bad, it could be worse. Pobox.com's blacklist and SPF based filtering nailed 13,000 messages on that account in the last month alone.