From: Vermont, USA
Well, you could always play it and find out for yourself. :-) But seriously, I've found the AI challenging and I know many others that have as well. Inevitably, any AI is beatable. However, based on our testing, the highest level AI in a fairly crowded galaxy is a tough opponent to beat.
There are also many settings that can be adjusted to customize each game. I like to play with a 100 star galaxy, 8 races, Highest difficulty, Planet Killers, Challenging Pirates, Aid Unrest all on. I've seen many of my friends fall victim to the AI with these settings. I have also beaten the AI at all levels, but not without practice and quite a fight. It still beats me from time to time, though I'm sure there are better players who have mastered the game and could kick me and the AI around.
Ultimately, as a player who has been through MOO 1 & 2 as well as many other similar games, I believe Starships Unlimited's AI is at least as good as that in other games of the genre.