I don't download extensions to make Firefox usable - it's near perfect out of the box. I download extensions if I want some more esotertic features, and most of the time I don't even bother with that (apart from Flashblock, which really should be part of the base distro).

I've long since gone past the point where I feel I have the time to nurse each program into usability by obsessive tweaking. I want programs that work fine out of the box. Firefox does, which is why hold it in such high respect.