Rated 5 out of 5 stars
There's a modified version that works with FF4 over at GitHub.
Steps to get a working FF4 dersion:
1. Download this version and save it to your disk
2. Download the source of the FF4 version @GitHub
3. Extract the downloaded zip and go into the "firefox" folder
4. Open the FF3 .xpi file you've downloaded in Step 1 with WinRAR
5. Mark everything in the "firefox" folder (Step 3) and drag it over to the WinRAR window (Step 4)
6. Confirm the "overwrite" message and close WinRAR
7. Now install this updated Add-on into FF4 (Drag & Drop the .xpi into your FF window)
I'm using roadrunner2's version for a while now and it works fine.
Hope this helps until we get an "official" update.