In an odd turn of events, it's actually become one of my CPs of choice, especially against Snake of all people. I'll divide this by stage.
Stage 1/Top of the castle
Uneven terrain/main stage gives us the slight advantage and disadvantage depending on the situation. Being on the left side obviously opens up many options, while fighting a character with long ranged attacks will put us as a disadvantage being on the right. Z-air, U-air, U-tilt/F-tilt angled up, Up B and Missiles of course all appreciate the cover provided by the low platforms, and even bombs could be used slightly less crapily than usual. The edges are both walls, so Samus has an easy time stalling out with Wall Jumping(you can even do that Spiderman Bomb thing if your opponent is dumb enough to wait for you/too scared to approach. The ledges can trap you ala FD lip if you aren't careful, however. Overall this is my favorite part of the stage, the ceiling is odd that we get utterly screwed, not too low and not so high we can't KO with D-air/Smash. During the transitions to and from the other stages, you can abuse the temporary floor to sneak in a few more hits than normal, or even a KO if you're smart enough(hold them where there is no floor when transitioning from stage 3-1, get them near the edge so you can Z-air them off the walk off during stage 1-2, and so on). There is more to this stage, but I'll try to leave at least something that other people can contribute. :d
Stage 2/Castle hall w/statues
Yes, the dreaded statues that eat projectiles. For obvious reasons, this is the least liked part of the stage for many, but I've grown fond of it recently. While it is true the statues hamper our spam game, I find the not-situational advantages/disadvantages to add up to a neutral or even in Samus' favor phase of the battle, not counting certain characters(coughDee3ZeldaMario/PTwaterguncough). For starters, the disadvantages don't just hurt Samus(and don't hurt her the most, in fact). Unless your name is Zelda, your projectiles are at the mercy in the middle of the stage as well(this especially helps me in the Snake MU, as they'll have to rely on C4's as their only projectile while we still have Z-air and bombs to a non-existent extent). The statues have actually helped me more than hurt me. For instance, several of Samus never-used moves could be used to destroy them and/or refresh move. Helps that U-smash is a multi-hit move. But this brings up my next point. Samus' moves last longer when hitting the statues, which more than likely can assist in catching foes with the lingering hitboxes(again, helps in multi-hit moves or just moves that cover a decent amount of space, like D-air/U-tilt/N-air/D-smash, and even Z-air), and this'll do wonders against any characters/opponents who rely heavily on spot/air-dodging. Lastly, the biggest advantage, I think, is how well Samus can maneuver here. Up B lands perfectly on the higher platform, you can use bombs to stall around high up on the stage, and against characters who rely on projectiles, you can keep away and Charge a shot while they approach either fearlessly(mindgames to the max) or reluctantly(though your mileage may vary). Then there is, of course, the constant fear of the Grapple Beam(yes either on ground or in the air) pressuring them to the edge, or a lucky grab leading to a B/F-throw KO. Overall, I'd say this stage is good or bad depending on who you fight here rather than it just being automatically bad for Samus. Keep moving, play aggressively not just defensively, and use the stage to your advantage.
Stage 3/The underground/Hell
So as mentioned above, this is considered the only good one for Samus. The tilts really help her edge game, as she has a much easier time recovering than most from under the lip. Z-air anybody under it and unless they are MK/R.O.B.(even then they are in danger) and they are screwed. The side boundaries aren't very wide either, so this somewhat compensates for the higher than average ceiling, also making it next to ideal for surviving as well as KOing. Get 'em with a tippered Z-air or a Charge Shot near the edge and they'll die, or have trouble getting back to the stage. On the stage itself, the tilting can also be helpful occasionally. When falling, for example, sometimes the stage will tilt enough to let you dodge their attacks by stalling with bombs, air-dodging > Z-airing them back(or semi-fully charged Charge Shot if it's handy), and the tilting helps similarly to stage 1 in terms of projectiles. Careful so that the protrusions/higher side doesn't eat your projectiles, though. Lastly, being the higher side gives your attacks a bit more range if you use them right. D-air towards the lower side, F-tilts angled either up or down, and retreating D-airs all get ab it boosted. All of this is situational, though, and similar to stage 2, the effectiveness of the stage can vary depending on character/player.
Overall/Overall
Stage is good for Samus, but she'll lose to characters who can abuse it better or if they're just better obv. You have to keep an open mind and not rely on things you are used to if you are CP'd here, but it'd do you a lot of good to learn the stage for going there on your own choice, IMO. The stage has the traits to be good for Samus, but that is on paper. Just like to make Samus work, you'll have to work to actually make the stage work. If you are very versatile, or your opponent is not, then this stage will keep you/them on their toes. Tis all in your opinion in the end.
10pickuptheslackguys'
