I played around a little with the current state of the master branch (something like 3.1) and give this experience report, intended for development.
I played civ2civ3 ruleset and since I was used this being lame I was pleasantly surprised to find AI activity largely improved and on a lively level. Research and economy of AI nations appeared stable and more prospering. One AI though seemed to have abandoned research completely and the nations stronger in research now tended to neglect defenses. There is less chicken running of various units in the land and instead more targeted action. A powerful ally of mine succeeded to cause (I surmise) revolution in a common enemy nation and it split twice into new nations, additionally he started taking over the weakened cities. Cute!
ERROR-REPORT: Unluckily, after the enemy nation split into two (revolution) there started a malfunctioning somewhere in the Diplomacy section (QT-client tab "Nations") causing the program to crash when the tab is being pressed.
There have been an array of fresh diplomacy undertakings, like stealing technologies and causing revolts. I was a little disturbed by a mighty hostile neighbour but since they suffered some defeats they retreated and resorted to technology stealing. I was delayed since I had to focus on military. There was a flood of early settlers' movement and colony founding in AI players, recognizable in many oversea locations. I had very little chance to keep up with them. Without the powerful AI ally I had, I would have been lost.
ASSESSMENT: I have two major observations:
A) Increased "heat" in the system of economies leads to accelerated speed in research in all nations due to diplomacy exchange or technology stealing (which both are good). In the years 600 A.D. the 4 most advanced nations had Gunpowder and Navigation (1000 years later). My recommendation: increase costs of technologies in general say by 20-30 %!
B) Increased powers of AI nations can easily lead to retardation in human players' development. Recommendation: the impudent benefits of AI players (cheating) concerning economy should be reduced in as much as their powers are increasing!