This is a good thread, guys.
However, one thing I can't find is how the 1.29f patch supposedly makes the AI value newer, more expensive techs more highly and if that compensates (somewhat) for the AI to AI trade rate on higher levels. I haven't had a chance to play much yet on 1.29f and I thought the game was really poorly thought out with the default AI to AI trade rates on earlier patches, that is, libraries and univerities were a poor investment on monarch thru deity, so I always set the trade rate to 100 before 1.29f, on all difficulty levels.
I think this change to vaule new techs higher is based on a quote from Soren, and it's not listed in the readme for 1.29f.