Joanna is a good dancer only in dances that don't require her to move her hips. I'm pretty sure my cousin's 2-year-old daughter could do a better job of executing the hip action required by the Latin dances. I think that Derek did lots of tricky choreography to try to minimize her flaws, for which he should get a little credit for being clever, but that doesn't make her a better dancer. I will say that I really enjoyed their futuristic paso doble, though. But also that I'm glad to not see Derek, Mark or Julianne in the finals (I'm also glad that Julianne is taking next season off as well, and that she broke up with Chuck Wicks).
I seem to be in the minority here, but I don't think that Kelly is that good a dancer, or that she's gotten that much better over the course of the season. I think she's clunky (not her size--her movements) and whiny and I'm not a fan. I do think she and Louis have a cute, sibling-like relationship, though. He seems very older-brother-ish to her.
Mya's the best dancer, but doesn't have tons of chemistry with Dmitry, nor does she appear to have much personality. Donny's a good dancer, but definitely the best performer, and he and Kym seem to really enjoy each other. I'm rooting for Donny, but would be okay with Mya winning, too.
