One thing i have noticed is the lag after late Classical (alot) inbetween turns lately, and then on. Even on a standard map with only 8 civs.
Another is that the AI are waaaay smarter than they used to be.
ONE civ AI goes directly towards military units of the highest caliber first and forget about the other techs, and in doing so are like 10-15 techs ahead of the human player alot. Making it impossible to keep up with the strs that HE has, and thus he has convinced other civs to be vassals to them and wipe you out after Renaissance era.
I'd hate to play with Barb World and with Rev on, if the above happen this way just playing a normal game, you'd never have a chance.
Just again like i said a couple of things i have noticed lately. And this is on Noble.