Looks pretty great, well done!

In Firefox 6, the knob of the speed slider appears at the top of the page, instead of inside the slider track. It looks like this is caused by having "display: inline-table" on the #time_slider element. That seems a strange choice, given that there's no child-elements with "display: table-row" or "display: table-cell". If I change #time_slider to be "display: inline-block" instead, the knob appears in the right place and works as expected.