what neighborhood(s) are you looking at?
this sounds obvious, but make sure you check that gas stoves, faucets, etc. are in working order when you're viewing. i neglected to do this when i changed apartments last spring. there was a gas problem that would have been a simple, one-day repair from coned. 10 months of no cooking gas and vitriolic correspondence with the landlord later, and 9 out 16 tenants in my building, including myself, are now in the middle of a tiresome court battle.
make sure the garbage area is well-maintained, especially if you will be moving above a restaurant, otherwise you are at risk for pests. i know people who have had mice turn up in their bathtubs, been sleeping and had roaches fall out of cracks onto theiir beds, etc...
the minute i moved to the city i sold my car. parking lots are too expensive, street parking is a major pain, and you pretty much can walk or take the train anywhere you need to go. i can't imagine going back to driving anymore.
i live in a pre-war, 4-story, no-doorman walkup and i'm extremely happy with it (legal battles notwithstanding). i think the pre-war buildings are more charming than post-war.
prices seem to be going down; a unit in my building opened a recently and its rent is $300 less than what i'm paying. i could have moved across the hall and saved all that money, but unfortunately it opened the day after i renewed my lease

if you know people in the city, you might want to ask if there are any openings in their buildings, word-of-mouth is a good way to find out about things.
happy hunting!