should probably be called dark grey

I love Dark And Black Theme.

On my XFCE desktop with Numix theme, this Firefox theme fits perfectly. There is no visible edge between window decoration and menu bar. I'm so happy I've found this.

I like how the dark grey gives the Browser a black-matt feel. Perfect

What I like:
I use all-in-one sidebar and this theme goes all the way down the page instead of just a quarter;
It is a subtle change that looks quite nice, and even the grey isn't too light (which is good because of how the min/max/close buttons are on my linux laptop).
Even though not solid black, it's a good dark theme; I also prefer it's simple solid texture as opposed to some of the carbon and other textures out there.
What I don't like: ...I'm not really sure, my previous theme was a solid black, but I think this is a good substitution that I do not regret. I also put it on my Windows desktop machine