I think what all the other guys have said already is correct, within reason, and I'll quantify that comment. After having huge amounts of success in other space/naval style combat games; the one thing I would say about ACTA and the reason why it is my favourite, is because of its scope and how much variety there is in both races and their ships.
Are the Centauri skirmish level ships any good???? Well that depends on who you are playing right? Of course it does! It also depends on what priority level you are playing. I'd say this:
If you are playing at skirmish level or below, like the others I'd probably rather shoe horn raid ships in, or go down to patrol level. I personally don't think the Centauri skirmish choices are good enough "all rounders" at skirmish level. For instance, if were playing at least 4 points at skirmish, I'd rather take two dargan or altarian, than 4 skirmish level ships for a number of reasons. Most other races seem to have at least 1 skirmish choice which a damn good all rounder; most Centauri choices seem to be specialised.
Now if you asking about the worth of Centauri skirmish level ships in higher level games, well thats different. Vorchans, normal ones, are my favourite and I can't understand why so many people have problems with them. They are one of the few ships in the game that can actually keep up with a whitestar, what they do when they catch it I don't know, but they are EXCEPTIONALLY fast and agile. I use squadrons of 3 vorchans, and throw them up the flanks, by now most of the people I play against realise that they must either dispatch some ships to deal with them, or suffer next turn, when they whip in from the flank and do some serious damage with their plasma accelerators. LIghting fast attacks from the flanks, are the way to use vorchans, don't bother trying to use them as mainline warships as it tends not to work.
Maximus I like for opponents with plenty of fighters, the maximus comes as a nasty shock, and general defence. Darkners are, as previously mentioned, excellent for backing up battlecruisers. Kutai I'm not sure about along with the morgrath; they are a niche kind I think.
My thoughts for their worth.