Have you played it? Everyone I know who has bought it has been disappointed. I'm resisting the urge for now.
I've been playing Civ 5 quite a bit. It's every bit as addictive as the earlier versions, but there are quite a few changes that you have to learn. You can't approach it like an older Civ game because they've tinkered with the mechanics quite a bit. For example, they've gone from squares to hexes, and there is no unit stacking, so you can only have one unit per hex. Also, units and buildings take a lot longer to build, so you have to be more careful in choosing them and fighting with them.
From reading some of the Civ fansites, the biggest complaint is in the balance of the game. Some countries and their military units are vastly overpowered compared to others. Also, I've seen complaints that multiplayer is buggy to the point of being unplayable, but I don't play multiplayer anyway.
I think the consensus of the community is that Civ 4, after its two expansions, was the cream of the crop for the series. They also expect Civ 5 to get there eventually after it's patched and balanced, but for now it's pretty unbalanced. If you're going to play it, be sure to visit a fansite like CivFanatics or one of the others to learn some of the strategies, because strategies from the older games don't work. Also, the fucking manual is a 200-plus page .pdf that's buried deep in the Steam folder on your hard drive.
I'm enjoying it a lot, but you really need to learn what they've changed and how to adjust to it.
