I've been playing Napoleon a bit recently. Went straight from Medieval II, never touched Empire, so I was a bit out of my depth for a bit.
Of course, I managed to solve almost all my problems by simply using more artillery. Though I am somewhat disappointed that despite taking a direct hit from an iron roundshot or basket of grape, there's never any ludicrous gibs.
I like a lot of the little things added, too. Simplifying the General/Spy/Assassin/Merchant/Princess/Diplomat/Priest dynamic was nice, as was letting Generals be simply recruited. The spawning of Armed Citizens makes a nice touch, so now you don't have to worry about a lone general running around capturing towns. Adding the towns, ports, farms, so on is a nice little bit of detail, so every region isn't just one huge city, but its own complete little economic and political entity.
One of my most fun battles was defending Vienna from a sizable infantry, cavalry and artillery attack, using nothing but a sizable force of Militia and a general. I carefully set out cavalry spikes, two rings of trenches, and anchored one end on the town with a garrisoned building. Ended up taking massive casualties, half the army routed, and barely any ammunition, but won.