Regardless of what spammers think of it, Spamhaus is very cautious about the IPs it blocks. The need clear evidences of almost exclusive spammer activity. Of course if this leak brought some useful evidences which weren't available before, guess Spamhaus did use them.
Yes, I never knew just how well SPF worked until a friend of mine tried to use the wrong SMTP server for an email to me (the side effect of mail programs like Apple Mail and Thunderbird keeping a separate list of SMTP hosts instead of properly and exclusively connect them to one account).
He immediately got a bounce, with a nice weblink to Spamhouse that explained what the problem was. Well, the explanation required knowing how email works so it was of no value to him, but at least it helped me to figure out what was going on :).