Thinking of moving to Belgrade from U.S.

Here's one more positive (esp. if you're black): You wont get shot dead by cops, for being black while minding your own damn business

Joking aside, public transport system isn't unreliable, there are buses, trams, trolleybuses, vans, taxis. The closer you are to the city centre, the greater chances you get for public transport. Usually you don't get to wait more than 5 mins for your transport. Also, there's a neat SMS system telling you how far (in stations and presumed time) buses/trams/trolleys are from your current station.

You can't live in apartment building where someone smoked? Those buildings get 5-20 apartments usually x 4 people in a household = go figure how many of them. And if someone behind their own doors and walls smoked, that would stop you from living in your smoke-free apartment? Really? Go ask someone who lived over there before 70s how that criteria sounds ridiculous. Just because someone in the building smokes, doesn't mean you'll sense it. Public spaces wise, bars, clubs, if smaller than 80m2 can choose being either smoke friendly or not, those bigger than 80m2 must have smoke only area, if they want to serve such guests. Smoking is banned in public services, official buildings, schools and work offices, unless there's a smokers only area.

I wont lie about other pollutants. Perfect storm for you would be winter (less people walking - more cars and buses, more coil being burned) + occasional high air pressure + no wind = you can smell it. Keep windows closed and suck it up. That being said, pollution wise, Belgrade is neither Beijing nor Luxembourg.

The bottom line is, if you focus on negatives you'll find every reason not to come/to leave, if you focus on positives you'll enjoy it here. The truth is somewhere in between.