Works great (hint on how to turn on) Rated 4 out of 5 stars
I was able to use a previous review to figure out that the "status bar" is called the "add-on bar" in my version of Firefox.
Once I found that, worked the first time with no issues.
It's a little awkward to turn on the add-on bar just to turn on JSD and then turn it off again (the "add-on bar" doesn't have anything I'm interested in 99% of the time).
For me, an entry on the Tool menu would be much better, or even a button on the "address/search" bar, where I've put one or two other buttons.