Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.
Buy it!

I'm not much of a gamer lately, but I'll admit, I have over 100 hours wrapped up in Civ 5. The dynamics are truly awesome and this game is super addicting. I bought via Steam, but If I could do it all over again, I would probably buy through the Mac App Store because (and I'm assuming here) I could then install on multiple Macs and because I don't like how Steam throws ads in my face just about every time I launch it.
 
It's on sale this weekend on Steam. I don't know what the price is in the US but here in the UK it's £7.50 for the regular edition ( 75% off ) and £10.00 for the deluxe one ( also 75% off ). Apparently the extra features in the deluxe edition don't work on a Mac though.
 
I got it on Friday via Steam (75% off for roughly $12.00 US).

It's worth $12 definitely, though I wouldn't buy it for the full price of $50.

CIV 5: Focused more on warfare and pure strategy. Little micro-management. One of the things I liked in previous CIV games was the complexity of actually working the tiles in your empire. In CIV 5, tile system has changed to hexagons and is slightly dumbed down. For example, roads are not necessary to connect resources. "City" tile improvements grant just one extra gold per tile and do not grow. I read a review that likened the interface to an iPad or iPod version. I agree with this.

CIV 4: Focus more on micromanagement of empire. In my opinion, more in-depth. If you're thinking about buying CIV 5, you've probably already played CIV 4.

I've only had the game for a few days and played for a few hours. I do enjoy it. It is an interesting experience. Not quite sure yet if I prefer CIV 4 or 5, put recommend you purchase the game sooner rather than later to get 75% off! With Steam you can play the game on Windows or Mac.
 
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.