I still disagree on your take on Jaime (and the other characters probably). I thought his change followed a very natural progression.
Self-centered jerk (no care about honor as everyone considers him a kingslayer) -> Captured by Robb Stark (takes him down a notch) -> Released by Catelyn (where she forces him to swear an oath not to fight against the Starks or Tullys again) -> Hand cut off by Brave Companions (he's now lost the single thing that made him who he was, his fighting hand) -> More awakened Jamie who actually seems to care about honor (and by this point we understand why he killed Aerys and it was, imo, justified).
Also, knowing what we know about Jaime and the circumstances around his murder of the king and how he has been deemed an honorless kingslayer by pretty much everyone, it paints the previous books in a different light for me. He becomes less villanous in AGoT to me because of this new information.
As for Arya, I also think the changes make sense. She's gone from the privileged daughter of a lord to living like a street rat, fending for herself, and constantly being put in danger. Over the course of the books, she's been forced to grow up very, very fast and she is constantly struggling with being the scared, little mouse she was and the tough, knows-no-fear fighter she wants to be so that she can avenge those she cares about.
But, I don't think we'll ever see eye to eye on that, so we might just have to agree to disagree.
Which is ok! Or maybe we'll sort it out in March with some SSBB. hehe