I tried the Booq backpack with my old 17" PowerBook and I can say that the Booq backpack is extremely well-made, perhaps the best I've ever seen. It's very well designed. However, the bag is also very big and rather heavy. Apple's 17" notebooks are the most portable in the industry, but the Booq bag made it feel huge!
So I returned the Booq bag and eventually settled on the Timbuk2 Track Day Pack:
http://www.timbuk2.com/tb2/retail/catalog.htm?categoryId=2&skusetId=122
This one is my new favorite. It's also well made (maybe not quite as durable as the Booq bag, but very close and a lot less expensive). Best of all, the Timbuk2 Track Day Pack is surprisingly compact and lightweight - perfect for your 17" MBP or PowerBook and a couple extra items.
Timbuk2's web site only mentions using the bag with the 17" PowerBook, but the bag also fits my new 17" MacBook Pro with no problem. They should update their web site. 🙂