This is exactly what I've been looking for since FF4 came out. Colors blend well with my particular setup. Nice & compact. Most importantly, it gives me a very clear & distinctive highlight of the bookmark I am working with in my Library. Most other themes seem to forget that element.
Overall it's the same stunning theme like before, very well overhauled and adapted for Fx 4. But the update button in add-on manager on bottom of page is totally out of visual focus and it looks like a bug there. It should be in top right area or at least somewhere on top half of the window.