Well, I forgot which episode it was (let's face it, most are pretty forgettable), but one of them was done by Production I.G. and is pretty good. The art style is similar to GiTS or Vampire Hunter D:Bloodlust. The whole '3d vehicles/scenery meshed with anime' thing has been going on for a while, though... SAC was hardly the first to do it. It's a cheap way to get the animation done, really.