This is all well and good -- and a similar post a few months ago relating how Malcolm Gladwell practices his lectures had much of the same information -- but to be completely honest, with the amount of multitasking most people do these days, almost none of the presentations we give are much more than information sharing via PowerPoint/Impress/Pages. The extra time spent rehearsing and preparing backup plans would be a complete waste.

It would be smarter for most people to practice their public speaking more generally so that when they're giving these innocuous, boring presentations they at least don't come off as buffoons (whether the demos work or not).