cmeik seems to have forgotten the allmighty Spizzico, a type of cross of McDonalds and Pizza hut. The food is surprisingly good, considering the price. =)

The city itself is good for only fashion and business. While it's entertaining for a day or two to see the Duomo and torture museum, spending any more time in the business district will lead to lots of money being spent on bars and overpriced cigarettes, all while becoming disillusioned about Italian culture. Any happy locals you talk to are either models or business people, and the only way to get anywhere social in the city is either money or fashion connections. Otherwise, you're restricted to the central park and touristy stuff.
Whether you're trying to score drugs or not, the central park is the place to get them. In the average time it takes to walk through it, you will be offered about three different substances on five occasions - cop cars "patrol" the park by driving through it at five miles an hour, often putting their lights on to warn dealers in advance. Keep an eye open for muslim gangs, as they're known to surround people and kick the effervestent life out of them with everyone watching.