F
Fuzzy Logic
I think the ones who wanted improved security have already switched
(and gotten it), and that further movement is/will be the result of
good word of mouth.
I would argue that no browser is secure and while it might appear to be it's
only a matter of time until a serious vulnerability is found. The best
practice is to find a well supported browser, keep it up to date, understand
it's security settings and use them. Finally practise safe surfing. Most
browser security incidents are a result of the person browsing doing
something stupid (saying yes to something they don't understand, visiting
questionable sites, etc.) not the browser itself.
Here is an interesting article on the current browser situation:
http://www.wired.com/news/print/0,1294,66726,00.html