MUCH preferred the previous version Rated 3 out of 5 stars

I am in agreement with the previous review. I was delighted with the previous look (v 1.3.7 & earlier) of this theme, it had been my theme for several months. Wish that I had not even OK'd the update to V2.
The previous version of the toolbar buttons had a subtle "pop." The new toolbar buttons are so tiny and low (NO) contrast as to be nearly invisible, a PAIN to use.
I really do not care if V2 is supposed to be a more "modern" look, it is neither as stylish OR as functional as the previous version.
Thank you for the tip in the reply to the other user about the about:config tweak that may be needed to enable re-install of the older version. I'd already (DEFINITELY) tried to re-install the 1.3.7 version but received a not compatible with FF12 error. A specific link to the relevant page in the support forums would be most helpful before I go to monkeying with configuration fine print, but a FF12 compatible version of the theme that regains the version 1.3.7 look would be even more helpful. ;)
Thank you...
[Adding on in response to developer's reply.] Please let me underline that my unhappiness with V2 is in direct relation to how much I liked the theme in its previous form.
As the reviewer before me also noted there are already other ultra-"clean" (read: sanitized, plain...) minimalist/"modern" themes available. In its prev. form BlackFox-Blue, was quite "clean" enough, but also had a bit of style, a bit of pop. A nice balance between style and clarity if you will. Now it is so overly "clean" that it's been sanitized beyond recognition, lost all it's visual appeal.
The new buttons appear to be different icon designs, and between the icon designs, the no-contrast look, and the yes, tiny, size, I have to stare at them for a minute to remember which is which. This look has rendered the buttons UN-intuitive, UN-stylish, and darn near UN-recognizable. Instead of trying to out-minimalize the minimalists and out-modern the modernists, please consider seriously the desire of a significant portion of the audience for an ALTERNATIVE to the cleaned-beyond-comprehension minimalist-beyond-belief look. There were already themes out there to fill that niche. ;)
I once used Gradient iCool, but that seems to no longer be supported, or kept compatible. BlackFox PRE-V2 was the closest I'd found after Gradient to a clean-yet-stylish look. But that was back when the icons had a bit of color and were actually recognizable.
Believe me, I've been dismayed by some FF modifications, such as removal of the fwd/backward drop-marker and a full-time stop button, etc., and have weathered those storms with the help to add-ons that allowed me to reverse those (other!) instances of minimalism-run-amok...

This review is for a previous version of the add-on (2.0.3). 

Every change naturally creates diverse opinions. It also happened to Firefox itself when switching to version 4. Anyway, once in a while we feel the need to go with time and modernize. The new style is cleaner and much more compact. Contrast may raise gradually according to feedback (contrast is a very individual since every machine has different screen, graphics processor etc so every feedback will be considered. As for the "tiny" buttons, they're also compact so precious space is being saved. An option to choose bigger buttons is in the pipeline so stay tuned ...