Well, I just tried the first few turns with the aztecs/apachians/maya's and its pretty cool if you ask me. One thing I immediatly noticed was the population growth being HUMONGOUS for the aztecs, with 9k people the pop growth was still 9%. This could prolly still be made higher using different kinds of temples and such, if you know what I mean, that can increase pop growth, or public health and stability. This is most likely because of the vast amounts of troops you can crank out, for fairly cheap, so your population can recover quickly enough.
I must admit, that I haven't played it all to much. I've been rather busy, with my birthday being yesterday and having party-ed all weekend and monday

You start with Hernan Cortes in the Americas Campaign, he told some kind of hot shot to piss off and went on to America anyways to conquer it whilst he wasn't allowed, and later on had an army send after him, which he took out fairly easy. Lots of other stuff happened as well, so I'm guessing those events will pop up in the campaign as well. I'll try playing muchos turn in a fast way 2night to confirm this.
Didn't disable the music btw, when I played with the apachians I did get music, kind of like some 'witches/shamans' chanting or something. It's a nice change from the normal music I guess ^^ I did quickly check out several units from the aztecs and the apachians. Some were pretty funny, you're gonna have to live without being able to use cavalry though. There's different ranks for example, and it's pretty easy to distinguish one unit from another because of the way they are dressed and have armor, or the lack thereof. One unit kind of stood out, they had huge 'arrow' like spears, which they used to throw at the enemy, doh, and they'd save the last one and were pretty good in storming the enemy.
There's really to much to tell though, simply summing it up would take a few pages
