Click Start to measure the response times of the click and vclick events in your browser, normalized by the mouseup/touchstart events (whichever is faster, depends on your device).
On the desktop, click and vclick should respond after about the same delay. On iOS however, vclick is signficantly faster than click because iOS puts in a 300ms+ delay for click.
jQuery mobile uses click events by default on its buttons, resulting in a slow experience in some environments like iOS. This plugin simply swaps these events with vclick events, so that you'll always get the fast response time.
Click on the button below to go to a page that does implement jquery.mobile.fastButtons and see the speed improvement.