I've put about six hours in to the game so far and have nothing but good things to say about it.
I'm nowhere near the Civ fan that many of you are here, but I see no issues with this game. I started playing CivII quite some time ago, but never grasped the full understanding of it since I was a bit young at the time. Awhile after CivIV was out, I remembered the game and after reading some rave reviewed I went out and go the game and its expansions. I played it quite a bit, however I didn't enjoy it all that much. As a newcomer, the game was beyond intimidating. The game was micromanaging to the max and there were so many concepts to learn so quickly, it was impossible for me to wrap my head completely around it. Now, I'm not saying this was a problem with the game. If I had bought CivIV when it was released, I likely would have had an easier time because all the additional content the expansions brought would not be there.
This is where I think CivV comes in. If FireAxis made a game with the same features as CivIV and more they would have been blocking out new players. To me, CivV is essentially a fresh start. They created a great base game for players to get accustomed to and then their going to release expansions to fill in the areas that CivIV is superior in. This allows for a quality game to be developed over a few years in order to widen their fan base even more.