Not great. The Atlantis levels are an annoying, obtuse, overly-difficult mess that has you frequently surrounded by waves of enemies -- a mistake, given that the combat is by far the worst thing about the first Tomb Raider. The two Egypt levels are miles better, but needlessly long (Temple of the Cat especially) and not more interesting than anything in the base game. I didn't hate my time playing through these levels, but they should be skipped unless you are a die-hard completionist.