Yeah. This is an abortion of a Metroid game. I came away from it more or less angry because of what I fear it represents for Metroid. I'll get to that. First, just a list of bad things:
1) They pretty much destroy what little character was given the Samus in the more modern games. I'm not saying she was deep before as she really was mostly a blank slate character, but she was also generally portrayed as confident. That's gone. Samus sort of becomes confident by the end of the game, but that's a problem as well. This is supposed to take place after Super Metroid and therefore more or less late in the series. Samus is a hardened veteran by this point and has literally wiped entire planets clean and completely eradicated the galaxy of the Space Pirates. Other M makes her doubt herself constantly and I don't get where it comes from. I can understand and would totally dig if she was contemplative and thoughtful, especially since she's more or less a loner. Apparently my image of her was wrong. Of all things in the game, I feel like this is probably the most unforgivable.
2) The item system is just sad. No longer do you actually find new gear (save for missle/energy upgrades and two minor upgrades). Instead, you start with almost all your gear and it's unlocked by a commander. This kills two things in the game. Story wise, it makes Samus look subservient to an old commander as, for example, she won't turn on the Varia suit in lava areas because the commander doesn't say so. The game claims this is in the spirit of cooperation with the commander and his team, but that's sort of a copout. That could have actually lead to something interesting as Samus, who is totally used to working alone, is forced to learn to work with other again. No, it's just an arbitrary way to control your progress. Granted, Metroid always did something arbitrary to keep you from your gear, but it also gave you the fun of going out and finding stuff. That's the problem here as there is almost no joy in finding stuff here (very unMetroid). Instead, you'll just get to a point and the commander will say something like, "Use your super missile on him" and then super missiles get unlocked. It's very anticlimactic and unrewarding. Any items you do find are just tucked in a corner or in a dead end hallway, much like an Easter Egg hunt designed for a toddler. Additionally, Samus always looks the same throughout the entire game. No new suits. That's just a bummer.
3) While there is something of a sprawling map, there's really no exploration. The game literally forces you along a path and will often lock doors that lead in other directions. I understand the old approach of showing you a way you can't get to without certain gear and that happens a little here, but you can't get back to these places once you do get said gear because the way back to it might be locked (again, very unMetroid). The world map is basically set up like a gimped Metroid Fusion. That is, a ship with a hub area that connects several themed "sectors." However, these areas are completely self contained with one way in and out (the main elevator).
4) Music is terrible (completely unMetroid). The problem is it basically isn't there. Most of the time the background is just low ambient tones, which is strange since this isn't an atmospheric game compared to almost all other Metroids (and most other games for that matter). I remember about three songs from the entire game and they all were used for very short portions of the game (like minutes). Two of these were unremixed things from previous games and the third was an overblown orchestra thing for cinematic. Not good at all.
5) For everyone saying it's a good looking game, I'd really disagree. Some of the inengine cutscenes look really good and have some nice things like field of view effects, but the game proper looks pretty bland. In fact, I'd say overall Metroid Prime still looks better in a lot of ways because of the detail, atmosphere, and just plain good design spun into those games. Characters might look a little better on a technical level in Other M, but environments and character designs look way better in Prime (especially if you're looking the widescreen version in the Trilogy pack). Not bad for an eight year old game. Bad for a two week old game on a slightly more powerful system.
6) Other M lacks weight. People are arguing that it tackles some "real issues" like PTSD, but I say those things are more the product of poor writing and people are trying to make excuses. Metroid Prime sort of had this grounding that made it feel like it could be a place that actually exists. Other M instead feels like a series of toys and definitely a game. Que was perceptive in his earlier predictions. The effect is that there's almost no immersion. I'm not sure if this is really a valid complaint as this is a viable way for games to work, but it's just very unMetroid.
The thing that has me worried is that I feel like this might how Nintendo views what Metroid should be. When they handed it to Retro, it might have been just a throw away since the series was never big in Japan and they figured something should happen with the series. Thankfully, Retro understood what made Metroid unique and interesting. With Other M, I'm seeing a lot of things that existed in Fusion. Metroid is relevant again thanks to Retro's work and now Nintendo wants to go back to things they had in mind from the beginning. I've read interviews where Nintendo's main Metroid guy basically says that they feel Other M is their chance to really show the Metroid they wanted to make. It reminds me of that whole Star Wars thing. Technical limitation kept Lucas in line and he produced something special. However, what made the universe interesting wasn't what Lucas liked and he screwed it all over when he got the chance.
There's also talk that the Primes may not be viewed as canon by Nintendo, which is just a real shame. While the Primes don't actually have much bearing on the story in Other M and don't get mentioned, the fact that Samus has been through that stuff and should be more of a veteran for it doesn't exist. Additionally, stuff like her ability to just look at a computer and take it over via scanning doesn't exist.
Overall, the worst thing about Other M is that it worries me that this is what Metroid will be in the future and that Nintendo doesn't think the work Retro did is worth keeping. Some may disagree because they don't like the idea of Metroid being 3D, but I feel that the Primes were probably the best example of making an old series work with modern mechanics while still remaining true to the original. It's more than just making it 3D, but about making what I envisioned in Metroid to be a believable place while making the core concepts of exploration and isolation feel new and fresh. They found the soul of the old Metroids and made a big game out of them. They also did this without making Samus a cliché or lessening her appeal. What little character they grafted onto her was one who was confident, but not necessarily a guns blazing badass. Other M's new take on the gameplay proper wasn't even bad, it's just the approach to the universe, the setup, to Samus, and the lack of care for details that are real problem. The Primes were a huge achievement and if Other M just set the new "standard" according to Nintendo then they just shat all over that achievement.