I've always been a fan of Sean Reynolds work -- especially on the Star Cairns adventure and the Scarlet Brotherhood supplement -- and he does a good job here as well.
He's hamstrung by the reprinting -- verbatium -- of the original adventure. It's the only module of the 'silver' editions that's reprinted like this, and I found that annoying. Why not spend the time to update the text to be better linked with the second (and much more useful) part of the book?
Greyhawk fans, especially those with campaigns set in the southeastern Flanaess, should definitely pick up this book for its detailing of the lost kingdom of Geoff.
For those who don't know, Geoff was overrun by giant forces during the Greyhawk Wars; the second half of this book is dedicated to kicking the brutes out of the realm.
The book details more than a dozen locations in Geoff, and plants plenty of good adventure ideas. I would have prefered to see some more information on the Grand Duke of Geoff, but hey, I can do that myself.
The biggest flaws I see in this book are the lack on integration with the original adventure, and the pathetic, somewhat inaccurate insert map. This book is crying out for a nice color wall map, even a small one, and I would gladly have shelled out a few more books to have one.
I'm running it in my campaign now, and it provides a nice distraction from the ongoing intrigues of the group's home city (and provides a good place for them to run to when their enemies and/or the authorities start looking for them)
If you're a DM who likes to add flesh to the skeleton of an adventure, then this is a great campaign supplement (and that's what it is -- a supplement, not a module). If you're looking to be spoonfed, or want to run something off-the-shelf, then its a lot less useful (esp. if you've run through the original).