This could be REALLY useful. You can speed up time to see how stuff would develop (say, you can build a bridge in 3 seconds) and run simulations on that. Combat training is probably going to be the least of it, I think - can't wait for this kind of thing to hit the private sector (at least, the technology - it probably won't contain the entire world, maybe just your neighborhood or something)

Although, putting it into the hands of the public might be a bad thing - considering that the internet started as a military thing, and it's flooded with geocities sites like "AmEeEs HoUsE oF kItTeNz" and "RJ'S COOL SIGHT". Knowing that you'll be able to download other people's "worlds" eventually (everything goes online nowadays) there are going to be people who build virtual monuments to themselves.. Like "BOBBYZ LEET WORLD"..