A friend bought it, I just played it twice so far...
In the two games I played it made the games themselves feel unique from each other. There weren't any new rules to learn per se, as the function/limitations/etc of the building are expressed on the building themselves. If you have played the base game a number of times as I have you find that your standard opening play is now for the most part obsolete. Both players have full knowledge of what special buildings are out before the game starts so the first couple actions take a bit more time then before as you decide your course of action and respond to your opponents play, but the gameplay for the most part is the same just enhanced by the random element of which buildings come out. I am sure with more play throughs I will be able to answer your question better though. Its definitely one of those expansions I wouldn't think about playing the game without though. It only makes the game better without taking anything away (unless you like static games where its more about perfecting your approach ie chess).
In the two games I played it made the games themselves feel unique from each other. There weren't any new rules to learn per se, as the function/limitations/etc of the building are expressed on the building themselves. If you have played the base game a number of times as I have you find that your standard opening play is now for the most part obsolete. Both players have full knowledge of what special buildings are out before the game starts so the first couple actions take a bit more time then before as you decide your course of action and respond to your opponents play, but the gameplay for the most part is the same just enhanced by the random element of which buildings come out. I am sure with more play throughs I will be able to answer your question better though. Its definitely one of those expansions I wouldn't think about playing the game without though. It only makes the game better without taking anything away (unless you like static games where its more about perfecting your approach ie chess).