Sweet stuff:
1. Bonuses for completing a social policy tree (reminded me of the bonus you get in Diablo II when you collect all the items from a set)
2. Getting my scout upgraded to an archer and becoming a super scout.
3. Samurai combat animation (And just samurai in general)
4. I LIKE the diplomatic victory. It is more like the economic victory in Alpha Centauri, but I think that there should be a victory condition that you can achieve by stockpiling tons of gold. Just like in real life, a modern civ that has stockpiles of cash can pretty much rule the world. See the US who runs the show by providing millions of dollars in aid to many other countries. This always reminded me of the way you get city state support by giving them cold hard cash.
5. Medieval ownage with Cho Ku Nus powered by upgraded great generals.
6. Having control over who your next great person will be. Really disliked the percentage model that was in civ 4. Strategizing for a GS and having a 95 percent chance to get that GS only to receive a GA instead was extremely frustrating.
7. Tactical combat. Small civilizations can finally hold off against huge empires by using terrain and chock-points to their advantage.
8. Ironclads upgrading to battleships
Not so sweet:
1. No religions or corporations. The game practically begs for corporations as something to do in the mid-end game if you're not a warmonger.
2. Sometimes your great engineer does not insta build a wonder. We should know ahead of time if the use of the GE will insta build the wonder and if not, how many hammers will you have left to fill. Its extremely frustrating to use up a GE only to have another civ complete the wonder.
3. Not enough diplomatic options. Perhaps there should be a "League of Nations" to create pacts and embargos and things like that, while the UN will stay as only a victory condition.
4. Caravels zipping in and eating up your highly promoted embarked units
5. since the last patch its possible to get infantry before riflemen. Kinda strange.
6. Not being able to get more than 30 xp from barbarians.