Although I haven't yet contributed to this debate, I have been reading what people have been saying (Nice into J-I-B).
Well here goes, controvesy time.
I don't rate Thud that highly for the following reasons.
a. It's hardly a laugh-a-minute book.
b. It seemed to me like a glorified commercial for the board game "Thud".
c. The spin-off "Where's my cow" was designed to "milk" Discworld fans of their money. It was awful.
d. I thought the point TP was making was too blantantly obvious and about as subtle as a brick.
Dealing with point "d", you have to bear in mind that this book was written in the same year as the London bombings and the ongoing debacle of the Iraq occupation. I'm surprised that nobody has mentioned this yet, but I believe the Deep down dwarfs are meant to represent fundamental muslims (possibly living in the UK and not even attempting to adapt to British lifestyle), while the trolls I believe are meant to represent the fundamental Christians (Bush & Blair etc).
I mean no rascist/religious offence from these comments, because as far as I can see, fundamentalism is wrong, which ever God you believe in.