Spoilers, obviously.
I just started reading this for the second time.
I think my biggest problem with the book isn't any of the stuff that Bill mentioned in the review, but was the fact that Pratchett KNOWS he's not got a lot of time left to write these books so he's cramming in everything he wants to talk about in this one. Sports, another Wizards story, orcs, Vetinari/Margolotta, the fashion world, office/corporate politics, all of it in one 350-page novel that I enjoyed, though I agree it wasn't his best.
When we didn't get to the fashion part until page 125, that's when I realized this book wasn't going to be as amazing as the others.
All that said, I just got to the part where Ponder Stibbons explains the succession part if Dead Men's Pointy Shoes doesn't happen, which basically sets up Ponder to be the next Archchancellor. And I was quite unhappy that they didn't use the Bursar more, but then I guess that's what Ponder's there for. I agree that Vetinari was FAR too loquacious in the middle of the book, basically acting as Captain Exposition. And the thing in the beginning where the urn shows up out of nowhere? Ermm... huh? I don't remember understanding that the first time around.
Trev Likely is yet another one of Pratchett's great characters, acted upon by the world and rising up to meet the challenge. Glenda is yet another strong woman who's far smarter than the ostensibly-smarter-than-her men for whom she works. Nutt is another Captain Carrot. Constable Haddock reminds me somewhat of Angua once she settled into policing. Dr Hix is the same joke over and over again.
Back in "Moving Pictures", when Ridcully was introduced, I remember them calling him "Ridcully the Brown". Then, later it was announced that he WAS a "Rowing Brown", indicating that the UU team mascot was the Brown. Now he's talking about how he (and I think the Dean, who will ALWAYS be the Dean) "got a Brown". A little confusing, but over 27 years even non-medically-affected human memory can't be expected to be perfect.
So... wrapping up Discworld, huh? I almost wish he could name a successor -- a writer to whom he says "I want you to go on writing these books, but only if you want to, and as long as I'm capable, I will answer questions and help out". I guess the big question is now: what's going to happen in the final book? Pratchett's going to have to do something pretty damn big to close out a series that we've all loved so much. My money's on terrorism -- someone flies a dirigible into the Tower of Art or blows up a train on the Undertaking. It would give us the Watch, Vetinari, the Guilds, Klatch or Fourecks or the Empire or Uberwald, the Wizards, the new guard (Moist and co.), and maybe even Granny Weatherwax. And of course Death and Susan will have to come back. Anyway, either that or personal computers -- he's already teased us with the Gooseberry; why not mobile or home versions of Hex? Also, I think the last book will be the end of Ridcully.
These are my thoughts. You may have others.