The new UI is streamlined, minimalistic, and functional. While every option isn't presented by default, all of the options are a click-away. Fans worried about a simplification based on Civilization Revolution should not fear. Notifications are also handled by an icon system. You won't have to follow laggy, scrolling text only to miss the blurb about your scout being killed by barbarians. Mouseover the icon for a quick overview of the event; click it to jump right to the point of interest.
In an effort to avoid the "stacks of doom" from previous titles, units will no longer be able to share tiles. The developers at Firaxis want the player to have smaller armies that cost more to maintain instead victory going to the player that bankrupts themselves by cranking out units. To this end, resources will play a major role in Civilization V.
In Civilization IV and previous entries, the Swordsman unit was unlocked once a player's civ had obtained iron. In Civ V, controlling one hex that contains iron will allow for exactly one Swordsman. Players may not build more until they discover additional iron or the existing Swordsman meets an untimely demise (or delete button).
Ranged combat also makes its debut as archers, previously maligned to a hard-counter role against certain units, will now be striking from a distance. They are practically helpless in melee, but can help soften up enemy forces without any fear of reprisal. This is extremely important as terrain attacking and defending bonuses (hills, rivers, etc.) are more important than ever.
Cities will now defend themselves with one unit able to garrison and lend a hand. City upgrades will improve defense and add different properties. City walls, for example, will not only grant a defensive bonus, but also allow your city to make a ranged attack. This frees other units up to roam the countryside and get tactical. No longer are your armies relegated to piling into your capital to repel invaders.
Fans of the religion system from Civ IV: you might want to sit down. Your beloved system is gone. The developers found that it added too much predictability to the diplomacy system. For now, the only system Firaxis is talking about to replace religion are city-states.
In Civ V, in addition to the ever-present roaming barbarians, will be city-states: neutral factions that are limited to a single city. If you befriend one, they might grant you a bonus every now and again; militaristic city-states might offer up a combat unit, for example. If you want an extra city, you can still attack and conquer city-states, but they might just be friendly with that full-on civilization you're eyeing for domination. You could find yourself in a war for your actions.
This all ties in to the new diplomacy system and improved computer AI. Firaxis hopes that the AI will play like humans. The AI are a bit more aware of what's going on this time around. Don't expect a warm welcome from Bismarck if he's spotted you massing units on his border; he's going to call you on this. Finally, the conditions for a domination victory have been stream-lined, requiring you to control only the capital cities of every civ, which should help make these types of wins more feasible.
Sid Meier's Civilization V will be released this fall for the PC and will promptly take over my life. I cannot wait to see more from this game. Hopefully, the next time I see it will include some hands-on time.