Rated 4 out of 5 stars
Congrats on this fantastic add-on.
Being able to customize the preview windows is great, but I have an issue for some time now. It happens randomly, but sometimes a preview window gets stuck and doesn't hide itself, making me have to restart firefox. Other symptom is just having the shadow outline permanently on the screen, restarting FF being the solution again. Using FF 3.6.10.