I am always puzzled by the attention paid to JavaScript execution speed. Obviously, it's important (and should be) to the people who are intimately involved wit

I am always puzzled by the attention paid to JavaScript execution speed. Obviously, it's important (and should be) to the people who are intimately involved with the maintenance and development of the JavaScript engines, but apart from that, why do so many people in the web business care about it so much? What sites and/or web apps are so JavaScript-heavy that they are bottlenecked by slow JavaScript execution? In most cases, aren't the speed of a user's network connection and the responsiveness of the web server itself far more important to the user experience of a web app than the browser's JavaScript speed? Is GMail on Chrome really a radically different experience from GMail on IE8?