I like the idea of the Slavery tech. I don't use mods, but that sounds cool. I HATE barbs and, hence, I am a very big fan of The Great Wall; thus Masonry is pretty much an early grab for me. I figure I make up the hammers and time by not having to build units to escort settlers/workers and defend improvements. And being able to divert barb armies onto my neighbors and slow their development is not a benefit to be underestimated.