UPDATED: 3 hours later a vulnerability has been published.
Google has just released an open sourced browser based on Apple's Webkit. I'm guessing it will be less than 48 hours before the first vulnerability is discovered. Since Safari uses Webkit it will be interesting to see if vulnerabilities found in Chrome will also affect Safari users.
Download Link: http://www.google.com/chrome
Article Link: http://www.powerpage.org/2008/09/google_outlines_chrome_web_browser_project.html