I think it’s a really neat library because it basically fixes all browsers so that the built-in DOM, events, etc work the same way. Instead of providing an API of its own, it makes the existing API work consistently and reliably.
– A fast implementation of the Selectors API
– Fixes broken browser implementations of the DOM events module including document.createEvent(), dispatchEvent(), addEventListener(), etc
– Supports DOMContentLoaded
– Fixes getAttribute()/hasAttribute()/setAttribute() (Internet Explorer)
– Implements a few other useful DOM methods like getComputedStyle() and compareDocumentPosition()
– Supports a variety of browsers including ancient browsers like IE5.0 (Windows and Mac)