The big, brand new feature comes in the form of city states - AI players who reside in a single city. They have propensities towards culture, food or warmongering and can be sweetened up with routine gold injections, ensuring that your generated currency has more intrinsic value than in previous titles. They can provide you with luxury resources – because who doesn't need more iron? – without the massive palaver of having to declare war on another civilization.
City states also issue you with routine directives, usually involving clearing out barbarian camps or fending off attacks, and favour anyone who helps out. An allied city state will declare war on your foes, too, which can often provide enough firepower to take the edge off any attack if you're trying not to grow your military. Diplomacy is largely the same as it's always been, so rest assured someone like Ramesses will usually end up warring with you. Buying people off is exactly what gold war made for.
But these features are just tools to facilitate a grander scheme of victory for your empire. They're piecemeal components of a wider, grander whole; one that sucks you in for 8-12 hours on normal speed settings. You can pluck them out and analyse them individually, and people will for years to come, but it's plain to see from such an early stage in the game's cycle (before DLC and expansion packs) that the combination of all these elements have certainly made this the most playable Civilization game to date.
2K now has three different factions to contend with: veterans, newbies and people crossing over from Civilization Revolution. That's three very different crowds to cater for, and it's impressive that the developers have done a fairly bang up job of handling everyone. A simple tutorial map has been provided as a delicate primer, and an exhaustive series of training pop-ups and advisor menus help segue Revolution (as well as rusty Civ IV) players into the swing of things.
Oh, advisors. I almost forgot: they're back, sort of. Your Science, Military, Economic and Foreign advisors are a mix of both pop-up tutorials and a screen of respective tutelage. They'll give you fairly basic (but pertinent) advice on what to do in order to achieve their respective desires. The cynical will condemn them for being pop-ups with faces attached, but personifying the advice ensures you'll always know exactly what each message is referring to.
Still, I'm just skirting around the edges of Civ V, giving you a few insights into the way I play and some of the things I've come across in the past couple of weeks. You'll get something different out of it. Everybody will – the random elements involved in generating a map ensures that each game will always have its own flavour, bringing various permutations of events and squabbles to the mix. I can only show you bits and pieces from my time with it, while trying to illuminate a set of catch-all differences that run through the game as a whole. But, really, it's those individual moments that make it so special, and you'll have to get those by playing it yourself. Who knows, maybe Catherine won't always be such a pain in the arse to you.
She probably will, though.