McPhee clearly has consistency issues, but she manages to follow up poor performances with good ones. There is certainly a large contigent here on the board who seem to be looking for reasons to hate her, so they pounce on every negative they can find, and ignore the positives. "Someone to Watch Over Me" and the other night's "Black Horse and Cherry Tree" were excellent performances, and more than make up for a muffed "Against All Odds". The fact is, she did well (but not great) with the Whitney Houston song you mention, but the judges unfairly savaged her for it, and for some reason, others continue to do so.
Do some contestants outlive their talent? Absolutely. I'm the one who mentioned Covais and Pickler, remember. I've never been a fan of Chris either, check my posting history. As for Bucky, I think he managed to hang on out of sheer work ethic and a genuinely "nice guy" personality.
Regarding Paris, my biggest problem with her is that she has absolutely no identity. Everything she did came over as a copy, and she almost always chose songs that were age-inappropriate. I think she's very talented, and that she'll have a good career in music. But she isn't "American Idol" material.
Of course, it's hard to really say that any of the competitors are truly "AI" material. This has been my biggest complaint about the top 12 this year. No matter who wins this thing, they're going to be deficient in at least one aspect of the "total package". Is the winner going to be another Kelly or Carrie, or will he or she be another Rueben? (Or somewhere in between, like a Fantasia?) I don't think any of them -- right now -- is ready to be another Kelly or Carrie. I do think that Elliott, Paris, and Katharine have the best potential, however.
But I don't see Mandisa's country perfomance as all that bad. I don't care for the genre but it didn't suck.
A better way of doing the show would be to pick a group and let them compete every week and then see who wins at the end.
One other thing about Paris....the identity thing is a catch 22. If you keep true to yourself then you get bitched at for being, as you say, one-dimensional. If you work the genres then you have no identity.
Paris will be great on Broadway. She just needs to grow up a bit.