A number of additions have landed that have helped to improve the performance of the engine. An element is reported as hidden if its inside a hidden element (something that wasnt possible before) The performance is much, much, better. The new Sizzle-up selector engine is starting to come to light as contributions from the larger JavaScript community come from larger JavaScript come in. It is now possible to call event.stopPropagation() or return false within a callback and have it stop the bubbling of the live event.”]
Source: https://blog.jquery.com/2009/02/20/jquery-1-3-2-released/