Good...but worth $20? No way! Rated 4 out of 5 stars

Would give it 5 stars for a good effort...but the suggested donation makes me wonder what this author is so proud of.

It does work...but not with Aurora. Can it? Will it? How much then? ;)

This review is for a previous version of the add-on (2.1.0.1-signed). 

Don't understand it - but like it! :) Rated 5 out of 5 stars

Seems to be blocking some content, but really can't tell. Don't have a clue as to 'what' it is doing "to" block...but as it supposedly blocks some spyware and tracking cookies, it appears good to me.
No real impact on the speed of windows opening that one can see.

This review is for a previous version of the add-on (1.5.1.1-signed). 

Thanks for the review.
See https://ad-ban.appspot.com/ff/help#how_does_adban_work for a simplified description on how does AdBan work. If you need technical details, then try investigating AdBan's source code at http://code.google.com/p/ad-ban-extensions/source/browse/trunk/firefox/components/adban.js .