Works in my version of chrome, does not work in my version of firefox (canvas appears, but no audio widget to hit play on - does firefox support only ogg and not mp3 maybe?) and of course ymmv.
Update: you can now change the zoom level with the slider below, and scrub by dragging left and right across the canvas pane.
Update again: apparently I can just host my file on soundcloud and embed their html5 widget and get timing information directly out of it. Woo!