Works for Me. Rated 4 out of 5 stars
It works for me, & I'm using FF 6.02.
If you are already logged into ImageShack, the uploaded image is loaded into your account---otherwise it just gets loaded on the server, but you still get the links. If you forget the link, you'll loose the upload & need to re-upload the image to get a new link.
It would be nice if it checked if your signed-on to ImageShack or not, & if not ask if you want to signon...