Last one in the bunch, even later than IE9, but something good nevertheless. Funny point in the article: FF passes the test not because of changes to FF, but because of changes to the Acid test :)
Edit: found the link: http://limi.net/articles/firefox-acid3/ So it was not wanting to put in partial implementations when a final spec wasn't complete yet just to pass a test.
Edit again: Even Firefox 3.6 now scores a 99/100
The change to the test is (to some degree) an acknowledgement that they were right on this.