Wow, I am glad such an expert weight in on this matter. How many different filters did you test and how did you test them?
me? none. but i have read reports off and on. basically porn still gets through, and lots of proper stuff gets blocked, getting in the way of research.
google gives some quick places for you to look, if you care to.
the internet filter assessment project.
The Internet Filter Farce.
Consumer Reports.
NCAC: internet filters public policy report.
EFF censorware page.
That last one has lots of links and explanations so you can familiarize yourself with the topic, so you can be always right.