Rated 5 out of 5 stars
Excellent addon. Allows me to visit US sites I haven't been able to since moving to Australia. Yes, you might have slight browser slow down, but if you only use it for when you want to surf certain sites, you can activate it with a mouse click, and deactivate the same way.
If you don't want to go for the paid version, you will get an Anonymox nag pop up at the bottom of your browser, not spam. I guess those complaining about the popup didn't bother to read what it said.