
The ability to zoom in and see individual units was nice visual candy, but it doesn't do anything gameplay wise. What I liked was how archers could defend any friendly unit they're near, firing back at the enemy if the adjacent unit was attacked. Fairly simple, but it added a nice element of strategy. The semi-random upgrade options were also nice. Every time a unit levels up, three upgrade options are given at random, which adds a little variety as opposed to a pure tech-tree approach. What might be an even better improvement is getting benefits based on what the unit had done - if they've been fighting in the woods, they get a bonus to woodland combat, or bonuses against spearmen if they've been fighting an army's worth of them.
That's something I though was a little off in Civilization 4, how you could assign points to any specialty you wanted. That gives the player more control, so there might be a very good reason they went that way. I sort of feel like prototyping something up to test if bonuses based on actual unit experiences would be fun.