So, in practice, s5 is almost but not quite the bomb. The dual screen thing worked incredibly well- I looked at the screen only once, and then only because I had to highlight some text on the screen. And the timer was nice. Unfortunately, putting the theme together was a PITA, and I had to do some grody hacks to make single-line slides work. If you are a hacker or otherwise don’t like OOo, and you or someone you know can make you up a stylesheet which does modern things (like lessig method or deeply image-centric slides instead of the bullet points s5 is optimized for) then I definitely recommend looking hard at it.