Definitely more awesome code out there but I think you're seeing that from a VERY vocal minority of developers who are 1) very vested in the OSS community, 2) love to share code and 3) are pushing to get the most out of JavaScript.

As I think John eluded to, there's a number of developers that don't fall into any of these buckets and a book like this would certainly be useful to them. I was with John on the jQuery team and I know that I'll be picking up a copy of this since I'm sure I'll find some nugget of awesomeness in there that will make it worth the price.