Good situational tech when used correctly. Rated 4 out of 5 stars
It generally works but I have to say I only really say it for others to use. Nobody else has physical access to my computers so for me I could care less about my history being seen. Also, for those who have others the sites they are on could be the real issue. If the husband or wife is in danger of finding the porn you probably need to file for divorce and land someone that you are attracted to... The fact is if they are determined enough there still will be tracks left for them to find. No single add-on can make it all go away. Furthermore your ISP is holding records for up to 18 months of your activities and who knows how much Big Brother is holding onto...
As far as cookies the real solution is to use a dedicated cookie manager. IMO Cookie Whitelist With Buttons is the best one for making sure that no cookies get stored without your expressed permission.
In short- this is good when used correctly and with reasonable expectations.