Hated the story. Absolutely hated it. Horrible, melodramatic, unskippable, Squeaky Samus cutscenes. The worst part though is that they force you to wait before you can experience more of the amazing gameplay. With the exception of Metroid Prime, this series has always been more about platforming than action, but this game pulls off more involved combat quite well. Now we no longer have to ask ourselves why Samus doesn't take advantage of her suit's super strength. The game still sticks to the tried-and-true formula of ranged combat, but grappling for a killblow is also an option. Watching Samus flip around in the air is also a joy. The bounty hunter's acrobatics look sleek and are easy to control, granting the combat a sense of momentum.
The game is split roughly in half between full 3D and semi-2D a la side-scrolling beat-em-ups. The transitions between the two are very smooth, and it is highly unlikely that you will even notice them when they happen. Classic backtracking tropes return as always, with every weapon from previous games making a return, even if slightly adjusted. The only real complaint I have with the game is that switching to first person to fire missiles (a state in which you are immobile and thus defenseless) is very poorly implemented, rarely leaving you an opening to use them in combat. The focus on action also necessitates a revision of the ammo system. Instead of finding more rockets, power bombs, etc. from enemies, you can now recharge them by holding down a combination of buttons. This sounds like it would make combat too easy, but it's balanced to be very difficult to do in combat.
Back to the game's one major flaw: the story. I'm not sure what got into Nintendo while they were making this game, but they somehow got the idea that they could easily make the jump from writing stories about plumbers rescuing princesses and bounty hunters killing space pirates to writing a story about Samus's moral recoil from having to kill the baby metroid, and how it relates to her emerging maternal instincts. Let me say that again: Metroid: other M is about the MATERNAL INSTINCTS OF A RUTHLESS KILLER. Clearly, someone at Nintendo has lost their mind. They might as well have made the game about Samus growing old and becoming a crazy cat lady. In fact, that would have been preferable, because at least that would be funny. This is just annoying.