I'm not as cocky about Firefox as I used to be, since we're starting to see malware and Trojans coded for it. It's still generally safer than IE, and better too IMO (tabbed browsing, among other things), but now that it's getting notice and market share, the script kiddies are starting to find its holes. No software is perfect.
}:-)4
Note that IE doesn't need to be running to be vulnerable; that's just one of the many benefits derived from tight OS/browser integration.
But, I am tired of hearing from the IE crowd, "Just wait until they target you...".