Just beat this. Overall, I'd say it was really good. My biggest problem with the game is design decisions made most likely due to the hardware. Since you have to hold the remote sideways, they ran out of buttons you could comfortably use, so they wound up mapping the dodge to the dpad. The problem with this is you can just mash the dpad and Samus will automatically dodge every attack and give you a free plasma charge on top of that. You don't need to properly time anything and it makes the game way, way too easy. If there were a dedicated button to dodging and the timing for it were strict (like Ninja Gaiden) I think the game would be a LOT more fun. But still, there's a decent variety of enemies and they all have good attack patterns. Bosses were very fun too. The puzzle sections were also pretty decent. And since it's a Metroid game, there's still tons of hidden upgrades and secret areas to find, so I'm not really sure what more exploration people are looking for. As it is, I think I've collected 34% of the items in the game, so there's a lot of junk to find if you're into that.
The story isn't THAT bad either. It has its moments.