For anyone interested in psionics canon in Eberron, I'd highly recommend this book. There are a lot of NPCs and political information as well as some weapons and feats that may prove useful. It seems a little bit of a throw-back to forgotten realms style regional modules.
Downsides for me was that the material was very vague or limited, geographically, but fairly detailed politically. For example, they'll spend a tiny paragraph for a whole region that is leaking chaos into Eberron in Adar and has a lot of fantasy potential, then spend 5 pages talking about a political group that really, after reading it, isn't very interesting or have clear goals or themes.
For crunch, the PrCs and quori-related stuff seems a little tame...a lot more flavor than bang. Enough of the artwork is mediocre to remove it from the list of strengths.
I think I would have liked the book to be...bigger. There is a lot of material to cover and a lot of it gets short treatment or no treatment at all, but still a good book especially if you are interested in non-Khorvaire Eberron, as I am.