Plain and simply the best entry in the series. If Legend marked Lara's comeback, this one definitely marks her triumph.
Underworld is visually stunning, and gameplay stands up to the awesome graphics. The puzzles are as epic as they get in an adventure game, and figuring them out takes a good blend of skills and thought. the camera generally behaves in a good, fluid way, and the fluid movement camera does a good job at showing you points of view that combines drama and usefulness in pretty equal measures.
Overall, gameplay It is not perfect, but it's solid and most importantly, FUN! Combat as been overhauled from the previous games and should be much more satisfying for players.
This is truly Tomb Raider at its best. And it goes on longer than Legend, which is great.
So quit reading reviews and just go pick it up and play it, you won't regret it!