There's exploration in the game alright. Like fusion though, it mostly occurs after you open the sandbox. Really, the game is basically like fusion in those regards, but still well worth it.
Rather than obtain upgrades and powerups, Samus retains everything she collected in Super Metroid, but due to the fact that she's working in proximity to other soldiers and innocents, she needs Adam's authorization before she drops a power bomb or something. Really, it works pretty much like finding them, you just aren't shooting a ball in a statue and touching something. Once adam gives you the thumbs up for something, You get to use it the rest of the game. This only results in two major oddities. One, You have to run through a significant portion of a lava zone without Adam's permission to use the Varia suit (although the heat does negligible damage.) Later, Samus gets to turn her stuff on at her own discretion, but does not activate the gravity suit when that would be handy. ...go figure.
There is music in the game, even some during gameplay. The argument regarding a lack of item fanfare should be approached with the understanding that *no* jingle is played at all when you get an item. So, they didn't replace it at the least. It just isn't used.
No health/missile pickups, aside from capacity upgrades, like missile tanks, and energy tanks. Debuting in this game are also three other items:
Energy part: HEY KIDS, REMEMBER THE PIECE OF HEART FROM ZELDA?? GUESS WHAT? 😃
Recovery Tank: When you run dangerously low on health, you have to ability to recover a small amount, using the same technique that you do for restoring missiles. These increase how much you restore. All that this technique costs is a little bit of time while Samus sits there helpless.
Accel Charge: these yellow tanks make the charge beam work faster. They aren't too common, but look out for them anyway. You'll be glad you did.
The name "Other M" seems to apply specifically to the plot. Consider who/what Melissa Bergman really is (I can't say it here), and it should make more sense. Also, consider the ongoing theme of maternity in this game. It was there in Super Metroid, but gets heavier emphasis now. "Other M..." "other M..." "M other" ?
Overall, I was quite pleased. The forced observation modes (OH NO HE'S DED, LOOK AROUND AND SEE WHAT KILLED HIM) need to go, but otherwise if Samus was given a traditional, solitary mission using this game engine, it would be golden.
I absolutely loved her portrayal, btw. I know it might not have been what other players expected or wanted, but going by canon info from the manga (yes it exists, and Other M borrowed heavily from it), Samus isn't a particularly cold brute. She's essentially a lady in a suit. Calm, compassionate, concerned, and very protective of those she cares about.