The changed the level design significantly. It shares the basic flow of the original game but the maps themselves are almost all drastically changed. You'll find plenty of areas from the PC version but just as many areas that are completely different.Whats different? A friend of mine gave me Doom 3 collectors for the original Xbox, but I just set it aside, since I figured it was just a normal console port of the PC version.
Most of the larger areas were decreased in size, however, but it still plays very well in its own right. It should be noted that it RAN very smoothly (solid 30 fps). I thought it was a neat rendition of the game and offered a different experience than the original.