I don't think that the characters were really all that inconsistent... I just think that they were growing older. If I look back on how much my personality and outlook on life had changed between when I was eleven and fifteen - not to mention those of all my close friends - I begin to find it stupid to assume that anyone wouldn't change.

Please point out instances where I was completely wrong, but most of the changes throughout the books, (particularly the last two) seemed like natural extensions of the characters into the fourth dimension.

Then again, I'm typically slow to see fault and quick to forgive...