I bought it yesterday.
Things added since the first that I saw:
- Money is acquirable from looting and such
- There are several shops around, such as blacksmiths, tailors and art merchants
- These shops add the ability to upgrade and customize your armor, dye your clothing, and get various weapons for different loadouts
- Health doesn't regenerate from nothing to full by itself anymore, only one square will ever regenerate as far as I know. Doctors are there to heal you.
- They seemed to have added some side missions that you don't necessarily need to do for the main quest. These are beat ups, races, and courier.
- There is achievements, and I believe they are acquired from various feats, such as diving off a huge building, as well as through missions.
The story line is great and progresses nicely compared to the first. The combat got some upgrades as well, you can grab people and slit their throats for example.