Editors' take: First-person shooters have always been hard to pull off on the iPhone, with its lack of tactile controls. N.O.V.A. was one of the better examples of the genre, however, and it's also one of the first to get a rerendered HD version for the iPad.
The game seems exactly the same to us, although with sharper graphics. The main difference: the iPhone version is $4.99, and this one is $9.99.
Even with the bigger screen, or perhaps because of it, we still feel FPS games are not a natural fit for tablets, although we do appreciate N.O.V.A.'s ability to reposition the onscreen controls to anywhere on the screen.