Very good addon. Has blocked multiple ads from many websites such as Yahoo!, Facebook and YouTube. Sure, it leaves a blank spot where the ad is, but I don't have to look at that ad, so that's a bonus.

EDIT: This new profile scanner has been a major annoyance when I try to make changes to my Google account or even make a new one. It will have a pop-up open in the middle of the screen and there's no way to close it. I'm not sure if this is intended, but it's annoying to say the least. Lowering my rating because of it.