Good, bad, so so? What does it have inside? :confused:
I've not used it, but it looks good on paper. Crunchy mechanics for running a dominion, backed by some feats, a new NPC class that interacts with the dominion rules, some prestige classes, and something resembling a straightforward mass combat system. If I wanted to run old fashion "build your castle then march your armies against other castles" high level D&D, using these rules and the core 3e books would probably work.
I think the system in the D&D RC works better for this.
RPGPundit
I reviewed this:
http://www.enworld.org/reviews.php?do=review&reviewid=2011119
I found it less that satisfying, but then, I have yet to find a domain system that really satisfying, so if you have got to have one, it might work for you.
The hiccups in scaling and vagueness/incompleteness when it comes to what different size settlements and fortresses actually represent in D&D game terms seemed to be big problems to me.