Being the Open Internet advocates that they are, you would imagine that most of us are generally big supporters of Firefox. So why then aren't more of us using it as our primary browser?
For me it's a simple feature in Chrome "tab to search" which frustratingly has never been ported into Firefox and every time I try to switch over the absense of this feature lures me back to Chrome as I'm just more effective with it.
Ref: http://www.danielfuterman.com/google-chrome-tab-to-search
What stopping you?
[edit: grammar fixes]
I actually love Firefox' dev tools and I really would like to use it - and it's not a bad browser at all- but as a developer all the small things add up (same reason why I cannot use Safari as my daily browser).