It's been a while since I read it, but I think I enjoyed parts of it, although it did feel as "too young" in places for me to appeal comlpetely. That can be explained by the target audience.
I really went through it quite fast (for me that is), and at times I felt that it was refreshingly lacking some of the Pratchett Tropes I got tired of at the time (I haven't read Discworld in a while because of this), but I don't remember the darker side of it all. Maybe I should reread, because "the revelation of the antagonist in the book being one of Pratchett's more revolting moments" is completely at odds with what I remember, but is a distinct selling point.

That is, after I finished the two books waiting for me besides the bed (HhhH and GRRM's DwD) and the one I'm reading now (Catch-22).

Thanks for the review.