Man, I know some of them are and I appreciate the hell out of the folks trying to keep it sane and posting actual criticisms, but that's not the rather large vocal group actually posting right now. The bitchy folk on the pro side of the fence aren't any better. Also any thread involving Steam makes me want to commit grisly murders.
I'd say as of right now, Civ IV is the better game. It's got nearly 5 years worth of patching and balancing as well as 2 expansions, so that's no real surprise. V does have a hell of a lot of potential and I'm personally enjoying it more than IV as well. This is due to various reasons, including removing a lot of the ridiculous microing and 1UPT. The slower pace of early game expansion is also welcome in my book. Definitely a work in progress as you said and I'm quite looking forward to seeing it blossom.
Now that I've played a couple more games to the end, more feature discussions!
The AI definitely needs some lovin'. The military aspect of the AI is pretty laughable They build all the right units but they get stuck in going back and forth between tiles instead of attacking, they move siege units right next to your melee units and you can protect a City State by putting a unit in each tile around the city and laugh at the massive number of enemy units that are surrounding the city and can't seem to recognize you as meddling in their affairs. In the event you get the AI to negotiate peace they are far too willing, for the most part, to give you a ridiculous amount of resources that regularly includes multiple cities. On the other hand I like that the AI actually seems to care more about troops on their borders and various other nice touches.
One complaint I see a lot on Civ Fanatics right now is that the AI is too "random" with their attitudes and declarations of war and such and that the civs don't have much personality anymore. I honestly think this just has to do with their difficulty in dealing with the AI without hard numbers backing everything up. I have definitely noticed rather obvious patterns in the personality of each Civ leader and differences in how they react to certain gestures. Bismark for example is a glorious dick. Always warring with City-States, always pretty friendly until it comes to blows but incredibly demanding even when you're allies. Very much in line with the Iron Chancellor. Montezuma is... well, he's Monty. Professional attack dog and dickbag.
I've pretty successfully made several enemies and allies with AI Civs and I like seeing the deterioration in a friend's attitude towards me as they realize that I'm getting too powerful for them to deal with and I edge (or rush, whatever) closer to winning. This especially becomes quite rich and when you factor in the City-States and all of the leaders relationships with them. I imagine it needs work (I'm not going to pretend like I know how well it's coded), but thus far I like that the AI is trying to win and I can't woo them past a certain point by playing the numbers game with Religion.
Great People are... well, they're pretty great. The Great Scientists might actually be too good honestly. Scientist give you a free tech completely, not just research points, so it's pretty ridiculous how quickly you can slingshot with them if you focus on it. Great Engineers are basically the same as Civ IV, incredibly useful for finishing wonders. Great Artists are a little more situational but are useful for getting a little bit of extra resource, but usually I use them for Golden Ages.
More later.
Edit - Note that I would like some extra details on other Civ's opinions of myself. Right now the only two indicators are Hostile and War. A simple Friendly, neutral etc indicator would be plenty for me. I'd like to keep hard numbers out of it.