i installed the K9 filter few weeks ago and havent had any relaps yet.
The thing with Pornography is that it is so easy to find that you almost dont think about it as a sin, it becomes a everyday thing, just a mouseclick away - but if you make it harder, more difficult to find, by setting up obstacles, blocking porn, and setting passwords for blocked content, etc - then you soon lose interest, becasue it is too difficult and too much job to find porn - man is a lazy animal, if its too difficult to get something - meh, nevermind then!
i can really recommend K9 filter!