Hands down the best Civ game yet. Like a board game of 6,000+ years of history.
I found the videos a little disappointing. I loved the Civ 2 wonder videos. Pictures and realtime movies of the Eiffel Tower and Universal Suffrage were some of my favorite parts of that game. However, I understand why the developers chose to stick with a more CG-look, as it fits in with the caricatures of the leaders of the various empires and the board game style of this game.
The board game kind of feel to CIV IV will be appreciated by many who love empire games, but also like RTS's. The units in the games also get promotions when they successfully defeat enemies, which adds in a kind of RPG element to the game. The graphics are well-polished and the music just adds to the feel of the game.
I had to upgrade my machine to a board with PCI-Express capacity (and an Nvidia 7600 GT), but I feel that it was well worth the investment. It's easy to get a handle of the game, but it takes a lot of time experimenting with tactics and strategy with the tech trees to master the game.