Thanks for the extra advice.
I've been playing Civ since II.
I've already started my first game in BtS. So far so good. I started out by reading SISIUTILS Civ IV Strategy Guide For Beginners and have been looking into the War Academy as needed.
Initial thoughts: coming from III, empire management has changed a lot. ex. Happiness slider is gone(I see you get this back with a tech, though), buildings are necessary for lux resources to provide happiness, sickness factor, roads do not provide commerce anymore, ect...
I've started out on Noble, Conts, all else default and plan to just work on empire management for now. I'll let the wars come to me. My two neighbors are a good 20-25 tiles away in opposite directions.
So far I'm digging it, so much new stuff to learn.
I also came from III and still play it sometimes. Two of the biggest changes for me is that if you have worthless land you usually don't want a city there in IV. In III more cities were always better. The other is diplomacy. I never had much use for getting the AI to really like me in III. In IV, getting an AI to Friendly gives a lot of benefits. However, with religions you have to choose your friends. Small piece of advice - don't be the only one in your religion!
Additionally, building maintenance is gone. You're right, there is a tremendous amount of stuff to learn, but it's a great game!