Some niggling problems were fixed outright. It always bugged me in previous Civs that you were rewarded for building roads in every single tile. In Civ V, roads and some other improvements have a maintenance cost so you need to pick and choose what your workers build wisely. Thankfully, you don't have to connect each resource with a road anymore, merely building the corresponding improvement within your borders does the trick. Finding strategic resources Iron and Horses is doubly important now because each resource only lets you build a finite number of units. For example, building a mine on an Iron tile might only net you two Iron, from which you can only build two Swordsmen. It's a brilliant system, because it forces the kind of strategic decisions that Civ is all about.
YES!!! This is always what I wanted to see in a Civ game. No roads on every tile is a nice touch, but I always hated it how having access to a single resource gave you an unlimited supply to it. Especially in the later stages in the game with modern resources like oil and uranium. We all know how important oil is in the real world, but in past Civ's all you or the AI's needed to do was secure one obscure oil patch and they could build all the tanks/jets/battleships they wanted. Now securing multiple resources will actually become strategic!
There's two other nitpicks I've always had that I wonder if they did anything with:
1. Difficulty levels. The way it's always worked in Civ you the player have on difficulty slider to move up and down, but behind the scenes there are two: one to gives bonuses to the AI, one to handicap the human player. So by increasing the difficulty, you simultaneously make the AI stronger while handicapping yourself, why can't you just choose to do one or the other? I always end up looking for stronger AI opponents, but hate the handicaps that get applied to my Civ at the same time. I feel like the only one though so doubt this changes in Civ V, but maybe I can mod it...
2. Take it or leave it Diplomacy demands. I tend to play with a lot of Civ's, so it gets tough to keep track of who's friendly with who. So it's a pain in the ass when my turn comes up, and AI Civ 1 demands I stop trading with AI Civ 2, I can't stop and check how this will effect AI Civ's 3-16 depending on who's friends with who. Rather you have to Accept or Reject on the spot, and can't proceed until you do. Why can't you minimize the window and leave the diplomacy offer standing, and give an offer when you're done your turn?
In addition to the resource thing, if these happen to be taken care of as well then Civ V will be perfect for me.