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Rated 2 out of 5 stars
I can't say it actually doesn't work with ANY sites, but I tried it with one - just a regular newspaper site - and it failed totally.
Also, it seems to install a status-bar icon that acts purely as a bookmark to the company site. That's not what I'd call an "add-in." The description says "just click" this icon to download. I had to click AND then paste the URL into the developer's site. (The site has an option to install a 'bookmarklet', which looks like a better option, to me.)
Of course, maybe I used it wrong... impossible to tell, because I can't see any documentation anywhere.
Bottom line, it may work for you, but it sure didn't work for me. On the positive side, at least it didn't seem to screw anything up...