The AI difference from Beta 5 to now is..well just night and day. Beta 5 as far as I'm concerned had no AI. Sure, the ships moved around and such but that was about it.
Now the AI reacts to things like influence starbases. It'll try to counter your influence star bases with its own. Some races will try to do a culture attack on you.
And when it comes to combat, no more willy nilly sending ships around ineffectively. They focus on specific goals and mass up for battles to take those goals.
They will identify a threat, determine what htey need to kill it and then put together the appropriate force. No more pathetic "Look, it's a lone fighter attacking my mega fleet".
In this example, I had a huge fleet massed for attack. I was pretty impressed with it. But then the AI massed an even bigger fleet. Some AI players go with fighters, others with capital ships, depends on the AI module.
One late game battle was pretty painful, my brand new "Debbie" (my wife's name) class battle ship was alongside a bunch of "Victory" (older model) class battle ship and the Drengin's fighters were powerful enough to take out the Victory class ships on their own. (speaking of which, I significantly decreased the upgrade cost on ships as a result).
Here's some cool battle scenes from last night:


If you look closely, you can see the Drengin fighters, they're itty pitty but they're nasty little buggers.
Also, the AI is MUUUUCH better at adapting its weapons. In Beta 5 the weapon analysis went like this:
IF (I am at war) THEN (Find most lethal enemy and counter their weapons).
Sounds good on the surface. But it's stupid. The Drengin and Altarians had been battling it out all game and the Drengin were finishing them off while I had built a huge fleet of ships that were perfectly suited for whacking the Drengin.
So the algorithm changed:
IF (I am at war) THEN (If my most lethal enemy is much weaker then me) THEN (Look at the most powerful military in the galaxy and factor their weapons and defenses into my counter measures)