After spending some time with this book, I can say two things about it with certainty, if you are against 4e, you shouldn't have bought the book in the first place.
Secondly, if you are silly enough to be convinced that there is no going back to the way things were, you deserve that "I just wasted 50 bucks" feeling.
This book passed the test, it was fun to read with and without the crunchy bits. The areas were well laid out, the changes were interesting (if a bit contrived here and there), and the realms are still a high magic playground full of incredible sights and sounds.
I hopped on board with 2nd edition, and muddled through 3rd as well. I never liked having 100+ gods, and dealing with the accumulated deitrus of 30+ years of splat was becoming more than burdensome. Life is about change. If you want to keep "your" older realms, nobody is making you shell out 50 bucks for this book. If it was getting a bit...stale for you, this is the ticket to a brave (and interesting)new world.