This week I finished playing Tomb Raider Underworld...
What I liked:
At the end of the game, you get to use Thor's legendary electro-bolt kick-ass overpowered hammer! Dudes go flying, and it's way fun.
Typically, games get harder and harder right up to the end. The player stays challenged up to the last levels and final boss... but I think it's neat to then give the player some overpowered weapon. I prefer this over what some games do: introduce some new type of gameplay (like a giant robot battle) which can be frustrating to learn and master all at once. If you worked hard getting to the last encounter, it can be a lot of fun to just blaze through it!
What I didn't like:
Tomb Raider Underworld felt like one overwhelming chain of puzzles to me. You get dumped in a room, have to figure out what to do, and where to climb in order to "solve the room". Crap controls aside, you eventually slog your way through... only to be dumped in another room with a boring puzzle to solve!
I noticed that I was really enjoying the motorcycle sequences, tossed in between levels. Not because the motorcycle is fun, I just needed a break! Uncharted (a far better game) has better gun play than Tomb Raider, and includes a fair amount of traversal levels (mindless walking or climbing from Point A to Point B). The parts where Drake pulls out his notebook for a clue to a puzzle are fun - because they're sprinkled in to supplement relaxing, fun, mindless gameplay.
Should you buy it?
Nope. Save your money and buy Uncharted or Uncharted 2!