I take it, from the example, that there are no manual transitions (i.e. you can't manually go forward or back in the slideshow; you have to wait for it to progress through)?
Topic on Extension talk:S5SlideShow
Sorry for not answering; of course there are manual transitions, pgup/pgdown and arrow keys work for switching slides. This also allows to use standard USB (HID) presenter sticks. That's how I usually use S5SlideShow in my speeches :)