But I do wish they'd explained it better, or had her act more messed up -- Kate running around scared and not really knowing who or anyone else is?

So much agreement to that. Even knowing Kate was messed up, I was bored with her story because it didn't really do anything. Didn't flesh her out more, etc. I like Kate, but it wasn't really about Kate, you know? It honestly felt like a pasted on plot device to explain why Kate didn't use her sudden superpowers to... capture the bad guys and go home. Something to keep the "Walter comes to a realization" story going. Amnesia would have been a lot more entertaining and compelling.