I LOVE NightShade Rated 5 out of 5 stars
I've used NightShade for about 11/2 years now. Simple, clean - very elegant. I've used it so long now, that, sometimes I forget that it's NOT the standard FF theme.
I've just started using WYZO (it's basically FF 3.5), and one of the things I love about WYZO is so many FF addons are compatible - especially 'my' NightShade.
Obviously, any theme, persona - anything - is a personal (appearance) choice. But, if what you're looking for doesn't distract you from viewing what's IN your vrowser, then NightShade is a definite winner.