I have played many 2.5/2.6 games and have noticed continual AI improvements. I play huge and bigger maps on godlike difficulty. Since 2.6 on godlike the AI has kicked my butt like 2 out of 3 times, so I dropped a level. The AI still wins ~ 1 in4 games (mostly because of an early bum rush and the good old RNG).
AI fleets are greatly improved. I no longer see every fleet ham strung with slow tiny/small ships. It is also utilizing some of my custom blueprinted powerful ships including picking my large support ships over the ‘standard’ support ships. The AI also seems to be doing better at what tech it researches.
I no longer see powerful AI fleets move to a tile and disband allowing me (with a much weaker fleet) pick them off one at a time
I also see it is now building specialized planets yielding production and research power houses.
Some room for improvement notes based on observations
1) Research specialized planets typically have no factories or cities making them slow to upgrage and not as powerful as they could be.
2) I see MANY constructors, freighters and colony ships parked next to AI ship yards even though resources, un colonized planets, and available trade routes are within well within traveling range.
3) While the AI is more aggressive at invading it is still a weak in this area. I see many times a good invasion fleet takes a planet and remain in orbit, even though there is an undefended planet right next to it (same star system)
4) Merc’s still need a rebalance post crusade.
I look forward to more of improvements and am ready to give more $ for a new DLC