I actually quite like this (plus Utopia - I see it as a three-parter), which is odd as this is my least favourite period of Who and the season finales usually sum up the ethos of the era. I agree with you about the Master, but it was probably done to parallel the hyperactive tenth Doctor. Or both were the product of the same zeitgeist - sarcastic, fast-talking, pop culture-referencing regular characters are pretty common on TV. I would have liked Jacobi to be the Master throughout, although Simm was cast first and I assume Jacobi was cast to provide contrast.