I finally bought civ 5 and played through a full game on default settings, except I used the earthlike map instead of Continents. I'm sure that most anyone who is interested in the game already knows alot about it but here was my impressions. The new cultural system was solid and I won a cultural victory by playing much the same way I always do but it was nice being able to spend the culture points on civics.
The new, one unit per tile thing felt natural but actually made waging wars easier for me. The cities were kind of tough but not having 30 units stacked on a single city made it much easier to wage war and yet felt more real. Surrounding the city and wail on it with archers instead of moving a giant stack in all at once just to stand a chance.
The tech tree was the only thing that felt oddly simplified to me. Many other things like the interface were simpler but didn't feel dumbed down.
The city states seam like a nice addition except that the map felt more crowded. I actually never built a single settler I took about 3 cities from city states and never allied with any for long. I got another settler for free at one point so I had about 5-6 cities and kept them for the whole game.
I'd say that Civ 5 is a nice remake and good entry point into the Civilization games, but it doesn't add anything new for me. Also it seams to take a decent computer to run well and there some major screen resolution issues that I just can't belive they haven't fixed yet. I keep editing an .ini file to try and get the game to display properly.
Also it plays the intro movie while the game loads so for a while the into isn't skipable and that can get annoying. But once the game is running its a solid civ game and keeps you addicted like all the others.