I find that Chrome's extensions are quite real, feature rich, and stable. The last time I used FF, massive memory leaks were blamed on "your extensions." Not to mention I'm not even sure which IETab extension is real anymore. One is dead, the new one is nagware, etc.
Oh, and I like that flash is sandboxed and autoupdated. I like a built-in PDF reader. I can't imagine going back to the stone age of browsers with FF or IE and downloading all the various readers and plugins for a basic web experience (Adobe reader, flash, etc).
I'm sure FF4 is good by Firefox standards, but Google is doing something very new with Chrome. The out of the box experience is stellar and end users are secure because they really have no idea how to update flash or adobe reader on their own.