Flexibility and availability of addons is certainly FireFox strength, although how it's going to compete with a Google backed webkit browser like Chrome long term is a tough one.Too little too late, I've really got used to FF and chrome, IE isn't going to win me back now. I have too many saved passwords in ff, and I'm used to the plugins.
I do use chrome for fast browsing occasionally
Outside of tech enthusiast communities I would guess Chrome is taking more market share from FF than IE because it directly targets the same market. It'd be a shame if Chrome pushed FF out the same way IE did to Netscape in the 90s