When deciding which service was best, no time was spared in answering all out questions and generally being as helpful as possible! This made making the choice of going with SpamTitan very easy! Since using the service our Spam Levels have been near zero, and where there are false positives the daily email makes it a piece of cake to release them / whitelist the email addresses! I would recommend SpamTitan to anyone.
There is not a lot i would say that i actually dislike! The only thing i think would be useful would be to write custom reports, that you can send as an email. For example all SPF rejected mails. It would also be useful to be able to override SPF protection for certain addresses only.
My small company were having a lot of issues with spam getting through our old filter and we also could not whitelist addresses meaning certain clients emails were hard to find! This is no longer an issue.