Firstly, TOA is the only expansion with non-functional AIs - DA and the original GalCiv 2 have no problems in that area. In addition to the AI problems, there are a large number of categorization problems in the new tech trees that results in poor AI research. Tolmekian's mod (mentioned above) and a few others fix the tech trees, but the only way to deal with the bad AIs (7 and 10 - 8 is not really flawed per se, it just operates differently) is to switch them to one of the functional AIs. That said, doing this should result in a much more balanced game - I disagree that it's as repetitive and predictable as enoeraew37 said.
However, I find the way the game has been completely abandoned very disappointing. I don't actually object to the idea of releasing an unfinished game, then finishing it through patches - this worked for the other GalCiv games. However, abandoning it before all of the bugs are fixed is downright disgraceful. Minor issues may be one thing, but the flawed AIs had been reported almost immediately after release, with no work ever done on them.
TOA is playable, and in my opinion quite challenging, if you tinker with it some, and the new tech trees arguably compensate for having only 2 basic AIs once you get them working, but the fact that you have to get the game to that point yourself is at best disillusioning.