I'm not sure if this will be the book that "fixes" 4e for me, but there's reason to expect I'll be a fan of this. The art makes up for the re-hashed art in the core books. The focus on one monster, perhaps analyzing behavior and ecology and the like, might make up for the abysmal Monster Manual.
Focusing purely on functionality, I could potentially get a lot of use out of this book.
This has some potential. The excerpts haven't filled me with a whole lot of hope, but maybe we're not seeing the juicy bits.
Holy Smokes! I didn't have an ounce of me that wanted to buy this book - even with the previews. Now I'll be pretty hard not to in the next few dry months... combined with the cool encounters the maps preview seems to indicate, I'm pretty mad at wotc for making me so eager to part with my money.