I setup 4 matches today to get a feel for the distribution of habitable planets and testing various things.
While doing so, they last one I have been watching the AI play.
Early on it tends to go for the closest planet. Not the best one, just the closest. I started on the edge of a scattered galaxy and instead of going to planets of 11-12 toward the middle, it went for two 8 sizes on the edge. Not what I would have done. It wasn't that it couldn't make it there, it could have. The other factions didn't get them for 15+ turns.
When at war
Too many rally points. There were something like 5 of them.
It never combined ships that were moving around into larger fleets. That seemed to only happen at rally points.
The ai will stand there while ships go by them to blow up the shipyard on a planet, THEN react. !?!?!?
Very slow to build and send transports. This results in wasted opportunities and worse, surrender to your enemies making them stronger! Instead of wiping out every shipyard, etc, take the planets!
It seems rare that it will post ships on a planet (or shipyard) on the front line. Instead there will be a couple of fleets standing around. Sometimes as the enemy came near, they went elsewhere when they could have probably beaten the fleet.
This is around turn 550 or so.
<Edit> I forgot to mention, NO RALLY POINTS OVER THE ENEMY BORDER! It just feeds ships one at a time to slaughter. </Edit>