Treaties seem pretty easy to get now. I can offer an Alliance to someone who is Furious with me and they will accept it. Not sure if it is a two treaty like the others are? Non aggression pacts are also almost 100% likely to succeed (again i'm not sure if this one is two sided either). The only time the AI doesn't want to accept my treaties is usually if I'm at war. Mind you my score is quite a bit higher than any of the dozen+ empires i'm in contact with so that may be influencing things.
I didn't notice any boosts from signing mutual free trade agreements with various powers, even when we both traded for it (free trade on each side). I did see the AI's power ranking shoot up (i think) but could not see any bump on my side (I wrote down the tech / economy numbers before hand, and also checked tool tips on individual colonies).
I used to never even have the option to trade these agreements (only give them) so I'm not sure how it is supposed to work. Its certainly nice to actually have the ability to make treaties with the AI, as I could never get relations high enough prior to even have the option past open borders and the occasional NAP, but it may need tweaking.
Also, when I set AI's up as teammates in the game, they do start allied, but being at war with one doesn't seem to mean you will be at war with the other. Not sure how its supposed to work in Vanilla.
Not really seeing any evidence of the AI terraforming to any degree. I've checked powers that have the same science as me and no dice, they are not researching it nor are they building it on planets (or at least they still ave planets available terraforming tiles 250 turns into the game, and havent researched the tech either).
For now I've just made a house rule to not research past the 2nd level of the tech tree to try to keep on even footing with the AI.
AI also does not seem to build its Hyperion buildings, which puts it at a pretty big disadvantage.