Better than ROB, definitely. Better than Kirby, debatable, but I'd say she is. But better than Mr GaW? No way. And Olimar and Pikachu is easily better than her. #12 seems about right for her.
It's about matchups though.
Better than ROB, glad you agree because this is pretty blatant.
Better than Kirby? I don't really see how it's debatable. She just does better against the top tier, Kirby gets beat worse than she does by MK and Marth, and also has bad matchups against ZSS, GaW, Olimar, and Snake. Those are all matchups that she goes even with or wins.
Not to mention Kirby's IC matchup is on par with ZS's Falco matchup difficulty wise. I just don't see how you can look at those matchups and say that Kirby is better.
GaW is an interesting character to me, because no matter how overwhelming the matchup and tourney data supports that he should be lower, many people are still clinging to the idea that he should remain as high as he is.
Matchups wise, he loses to MK, Snake, Diddy, Marth, and ZSS. That alone should be enough to show you why he is a B tier character. He's good for what he does, but once a player learns the nuances of playing against GaW, they shouldn't be loosing if they are using one of the above characters, and unfortunately for GaW, those nuances aren't very difficult to figure out and abuse.
I agree that Pikachu is better than her, he has an all around more solid game plan, and some abusable mechanics that give him rediculous advantages in some ways.
Olimar is difficult to gauge as well, I personally feel he is slightly better than her though he definitely should be in the same area of the tier list, within a spot or two. He does have a pretty terrible MK matchup though which really hurts him, as well as some random bad matchups with Luigi (can't really understand this one), Peach, and ROB.
I already posted my list a few pages back so I'm not going to relist any of it, but suffice to say that ZS is definitely better than Kirby, GaW, and ROB, and her placement will hopefully reflect that in the next list. I don't know if she'll break 10, but hovering around that spot is definitely where she belongs.