The earlier announced Civilization V Expansion Pack Gods & Kings gets explored more in dept by online game magazines Gamespot and Kotaku.
Both sites discuss the unexpected XP with Ed Beach, Lead developer of Gods & Kings.
The new game elements are explained more in detail.
Religion "[i]s designed to be an extremely flexible system that can enhance all types of play styles through a series of small benefits." While the very popular religion system in Civilization IV was political correctly implented, and all religions had the same benefits/backlashes, it will in Civ5 be introduced as something that actually does make a difference: "Civilizations starting near the coast may wish to purchase the God of the Sea belief, which grants additional production from fishing boats; while mountainous civilizations may prefer the Stone Circle belief, which generates additional faith from stone quarries."
It seems like chosing a specific religion does have an impact on your play style, but only for the first part of the game, Ed Beach tells Kotaku: "The religion game kinda happens through the first 2/3 of the game and then kinda naturally tapers out,"
The Kotaku article teaches us about the apparently complex system of religion. There are different types of religious units that all play their role in different layers of religion. "There are four categories of beliefs: founder beliefs, follower beliefs, enhancer beliefs, and pantheon beliefs. Each category comes with its own specific bonuses — one bonus, called "Goddess of the Hunt," gives you an extra food modifier. Another bonus, 'Holy Order,' allows you to buy missionaries to help spread your religion around the map."
Espionage especially seems to be designed for Single Player, MP fans will discover to their displeasure: "You could do this in previous games. What's unique about the spies in Gods & Kings is that you can use them to crack open the brain inside your computerized opponents, revealing the AI's deep, dark secrets." which does sound like an interesting and very useful expasion to the concept of spies. It actually makes spies more like what they really are: information gathering people.
Both articles are an interesting read. The Kotaku article especially displays a very enthusiastic Ed Beach. That's a very important part of game programming: having fun in what you're doing and being enthousiastic about what you're achieving.