You gotta love competition between competent and confident engineers. Instead of criticizing and denigrating the competition's accomplishments Mandelin congratulates and analyzes the V8 team's successes.
I remember when Chrome came out, their team said that they weren't trying to mess with Firefox, and that hopefully by keeping Chromium open source, they would enter a mutually beneficial race to create the best possible browser.
I'm glad to see that both Mozilla and the Chrome team are talented and mature enough to accomplish that together.