I just found out there's a DirectX 9 version. So my computer can actually run it.
Thank you Sid Meier, I think you may have just ruined my Ph.D.
Played literally about 40 turns in the demo as I need to get some sleep (early-game is about the only time I can escape the lure of the Civ

) and some of it's good. Combat is quite different, but in a good way, and it gives you a breakdown of combat stats if you mouseover an enemy unit within range, and you don't have to stuff your city full of units in order to avoid losing it, they have HP and ranged attacks. Interface is much sleeker, very easy to access reminders to queue up a new research project or production item is good. Culture is now coupled to the government/values types, so you can unlock a small tech tree of upgrades (some are mutually exclusive, e.g. freedom and autocracy can't be used together) but each unlock/tech tree upgrade increases the cost of the next one. Not a bad amalgamation of the two from Civ 4, without all that evangelism nonsense
What I'm not liking so far is they nerfed the city screen. It just feels...wrong, like there's tons of info missing. They've stripped it back to pretty much the resource map and a very short production list and governor options. Happiness is now a civ-wide stat rather than a per-city stat.
I think they've gotten the best bits of Civ in it - but I'll be honest, I'm enough of a nerd that I love the micromanagement and that seems to be quite cut back. I'm pretty sure I've had games of Alpha Centauri where I have so many bases and yet micromanaged all of them to the extent that I was taking about half an hour per turn. Had the most awesome economy ever though

I'm not sure what in Civ 5 would top that for me.