
3 things I love about this game:
1. The puzzles and pacing (at least so far). It's a first person shooter but there's also a lot of scanning for information, figuring out puzzles and exploring the world. The combat is not overwhelmingly difficult but it is challenging enough to be fun.
2. The controls are quite fun. When I first played this demo at E3 2006, I really liked the grapple control (hold down a button on the nunchuk and flip your wrist forward to throw an electrical beam at a door, or a shield on an enemy, and then just pull back to rip it off). I still like it. I also love jumping in this game much more than in Metroid Prime Hunters (where it was often frustrating to jump up on platforms)
3. The graphics and audio are very immersive and well done. For example, when you're wearing one of Samus's visors, you can see her eyes reflected in the visor, just barely. I didn't notice that at first and was like "what is that"? It really makes you feel like you're playing as Samus to see that (and makes it more obvious that she is a woman).