Well, Prime really just took Metroid and made it 3D...which was not at all an easy feat, and it did it amazingly, but it didn't really change the core gameplay.Maybe it'll be refreshing to see something new added to a Metroid game...
Kind of like with B/W, they're adding rotation battles and slightly changing that battle formula. Team Ninja is adding something new to the Metroid franchise... maybe it'll be a hit. Prime did it really well.
Metroid was never really about the combat, though -- it sounds silly to say that, given how abundant enemies tend to be and considering that boss fights occur regularly, but the focus tends to be on the puzzle/adventure aspect -- enemy fights are usually more about finding the weakness and exploiting it than just piling a bunch of Power Beams into them.
But with Other M's big deal out of finishing moves and such, as well as the fact that the health system is too close to the current FPS health system for comfort -- enemies no longer drop energy, you can merely "focus" anytime you're not fighting an enemy to restore energy -- I'm a little nervous about that direction.
I'm hoping that they're just trying to make the trailers flashy with all of the finishing moves and Other M turns out to be an excellent game. I still intend to get it on release date and am looking forward to playing it, I'm just sort of skeptical. And really, I'd rather be skeptical than hyped, because it makes it less annoying to wait for the game, and if the game doesn't turn out to be stellar I won't be disappointed.
At the very least, the plot should be interesting.