Very useful, smoothe, and nice looking. I've used this in mods for computer games, and I might use one like it in a game I'm creating.
Expect a large pack of paintball bunkers soon to save money, if you want a lot of 3d paintball bunkers.
I recomend using a free 3d-model application called anim8or (google it). That is what the .am8 file is for.