I just finished reading it, and I definitely enjoyed it. Liked the whole universe, the concept of the T'sel and the people of Tyss. The pacing of the story and the slow revelation of what's going on kept me reading. Overall I was reminded of both Starship Troopers and Foundation, which is a pretty strange combination for one book to make me think of -- but it works.
There were a couple of things that bothered me. First, the implicit gender division of labor in both the T'swa and the Ilyrians. Doesn't bother me that it's there, just that it's never explained/treated as an issue. Everything else in this universe that is different from us is, if not explained, brought to notice. But why are all the T'swa mercenaries male? Especially since they pick them young, based on natural inclination. I can see an author saying that women are different, never ever having the inclination for war. Or that they need to stay home and have babies, and therefore are forced to develop an inclination to one of the other activities. Or any other explanation that would make sense to the society. But the way Dalmas completely ignores the question was a blip of annoyance in my enjoyment of the story. Also, no government officials that we see are female, except secretaries and those of low rank. Again, why? I doubt that a preference for men is written in Standard Management.
Anyway, I'm definitely going to hunt down the next book in the series.