I use Google Chrome because it has been extraordinarily faster than Firefox 3. Firefox used to be my browser of choice after I took forever to leave IE because FF didn't allow much user customization. But though it was great at first, it really got the resource bloat and had become unusable, taking way, way too long to invoke, too big to keep running, it wouldn't even load pages quickly, even with no addons - I don't know WHAT happened to it, so I went to Chrome. I tried out FF4 last night and it does seem to be a big improvement and step back to usability, but I probably can't go back from Chrome, but I might use FF in tandem with FF4.
The main issue with Google Chrome is privacy. They tell you up front that they can note your browsing patterns. I also don't think the speed is that much of a difference between browsers, what matters is the system you have and the speed of your internet connection.