Rated 2 out of 5 stars
It appears to mostly work only on large, established sites. I've been shopping for days and only about 10% of the product pages I viewed were indicated as being valid product pages. Sometimes I click on the image link on a page and it will allow me to add it from there, but that's useless, it's just a link to an image. There is also no way to customize the wishlist entry. You can't tell it what image to use, or in my case, it doesn't show any images.
I would like to be able to add items from my wishlist page using the product's url. At least that would be a workaround.
Also, at no point did it ever add a button on a product page, only the toolbar button (FF 6 and 7). That doesn't really bother me, it just doesn't work as advertised. Overall: disappointing.