Unlike Steve, I did not find this story particularly plausible. Ok, sure, the group who was in power did some nasty things to stay in power; that's standard fare. It's the rest that has me shaking my head.
So, we're at war with an alien race. I know! Let's go colonize their worlds! And instead of an invading force, we'll send a generation ship full of colonists. Brilliant!
Then, when they get there, it turns out their enemies had posted a "trespassers will be shot" sign in that region of space and, true to form, started shooting. But! They would fail to destroy the vigilant colonists, despite the fact that the ship had been parked in orbit for 300 years, cut off from reinforcements and resupply, while the Mutts had the resources of an entire world at their disposal.
Back on the Centauri, the group in power has somehow managed to maintain that power despite gross incompetence. I mean, they left their figurehead, the Admiral, who was opposed to their plans, in control of the master switch that would ruin everything. Miraculously, the impotent admiral would fail to flip the switch, instead leaving an elaborate trail of breadcrumbs for an enterprising protagonist to uncover so that SHE could flip the switch. Naturally, they would not destroy said evidence, or even bother to lock the door that contained it. For 300 years, that door actually remained shut, with no safeguards in place to keep some bored teenager from breaking in on a dare (to say nothing of disgruntled ex-navy).
And the Mutts! If we could only talk to them, I'm sure they'd understand! We'd suddenly become enlightened and start calling them by their politically correct name. The conversation will go something like this:
Mutts: We hate you. This is our world, and if you don't go away we'll kill you.
Us: Actually, we just wanted to live here. Pretty please?
Mutts: Ok.
Shall I go on? This story gave us a weak plot, weak characters, and weak ideas, taking potshots at religion along the way. So lame.
Despite what I just wrote, I didn't hate this story. It just didn't give me much to like.