I behave - no spoilers here
From Amazon I read that Harry Potter and the Order of the Phoenix is over 255,000 words compared with over 191,000 words in Harry Potter and the Goblet of Fire. And the new book is 38 chapters long, one more than Harry Potter and the Goblet of Fire. So already in numbers, you get more for the buck.
I got my book the day it came out and finished it within hours...I couldn't put it down. It was a great read, despite its darker tones. Warning: there is a significant death in the book and it actually made me cry!! This was a fantastic book!