I'm pretty excited about this book, but then I was excited about the books that got canned as well.
I think there's some legitimate concern from the anti-essentials folks. My group is not anti-essentials per-se but we have been going in this campaign for longer than the existence of essentials, and a lot of the stuff is just plain incompatible. So, for example, if they make mostly powers that key off of mage schools, my pre-E wizard can't take any of those powers.
Of course, we just invited a new player and since we were high level and he had never played 4e before (just 3.5) i encouraged him to make an essentials martial character, so now we have a mix.
Ultimately, if a hardcover is going to be successful, well-recieved, and actually SELL, it has to have some things for everyone. This means essentials and non-essentials stuff, and stuff that works equally well with both.
That being said, there are some pretty obvious shortcomings: no shadar-kai, no shadow themes, and no rituals. I'm wondering if the table of contents was meant to ferret out good candidates for the first wave of dragon articles but... lately it seems like they're having a hard enough time keeping up with a month worth of standard content much less supporting a book.