Now this is definitely one of those "your mileage may vary" type reviews, so take all this with a grain of salt. But after playing around with Chrome for a couple of days, I still don't see what those 18% of users are so enthralled with. One of the big drawback to it originally was that there weren't very many add-ons available for it, and that's one of the great features of Firefox. You can pretty much make it do whatever you want via add-ons. That situation has improved significantly over the last year, as there are now plenty of add-ons for Chrome. But still I found a couple of my favorites (Download Helper and Tab Mix Plus) not available for Chrome, and at least one other (IE Tab 2) not as full-featured as it is in Firefox. Plus overall there's a general lack of ability to customize the Chrome interface the way you can Firefox. For example, in Firefox you can control when tabs open in the background and when tabs open in new tabs -- but that functionality seems to be lacking in Chrome. But if you are the type that prefers a "lean and mean" interface, and don't have all that much need for added functionality via add-ons, then I can see how you would like the very clean and minimalistic interface.
The other selling point for Chrome that you always hear about is speed, speed, speed. But alas, I didn't see that with the initial release and I still don't see it. Yes, sometimes pages will load lightning quick -- but other times they will load painfully slow. In fact, on an older notebook computer, i was often getting the "script has stopped responding" message with Chrome as a page was taking too long to load. On that same notebook, I never see that message with Firefox. Maybe if you put a stop watch to it and timed a bunch of web sites, Chrome might come out the winner by a fraction of a second. But for all practical purposes, what I saw was a push between the two on performance.
Bottom line, as far as I'm concerned, I'm sticking with Firefox for the time being. More functionality, more easily customized, just as fast, and perhaps a bit more reliable.