jQuery's own code is not so developer friendly, sure, but that doesn't change the fact that it has revolutionized JavaScript development in the browser for a lot of people. Before you criticize it, it also helps to understand jQuery's design goals: to be small, to be fast, to get out of your way and just "do what you mean".<p>A lot of its own code is hard to read exactly because it makes the code that uses it ridiculously compact and easy to read (e.g. liberal use of function overloading). In order to keep the library small, some of this code is not as clear and verbose as it should probably be.<p>However, jQuery is made by people who live and breathe JavaScript code. They use patterns that can look utterly foreign to people used to more conventional imperative languages (like logical operator short circuiting), but which are actually more readable if you know what it's doing.<p>As for performance, he points out a lot of things like "creating tons of functions on the fly" and "instantiating new objects for everything", but he doesn't actually prove that any of these points cause performance issues. It should be as simple as rewriting the code to get rid of these 'obvious' deficiencies and then benchmarking it. Which this person has not done.<p>I'll trust John Resig, the guy who is being paid by Mozilla to work on JavaScript full time, over some random internet dude with a chip on his shoulder.