Sarajevo trams always an adventure in Bosnia! Depending on the day, time and just sheer luck a tram ride can be quite the adventure. Some of the trams predate the Bosnian war and look like they survived daily shelling and sniping attacks. Others were donated by the Japanese (and some others) after the war and are modern and quite nice. You can pretty much tell what your tram ride will be like before you step on it. They can be quite crowded and unsafe, this is the number one place for pickpockets in BiH.
Some of my Sarajevo friends tell me only women pay for the trams in Sarajevo, I would suggest to visitors to remember to pay the ticket costs though as they are negligable and much less that a ticket from the Policija. Even though they are not heavily policed, they are checked from time to time.
Generally though they are safe, I have never had a problem on a Sarajevo tram, I am always careful when travelling abroad and in crowds. It is always a good idea to be aware of your sorroundings no matter were you are.
The tram service in Sarajevo is generally good and covers a large portion of the city from the downtown heading out towards the airport (but doesn't run to the airport for some odd reason).
besides the taxis which are pretty cheap it is a favored form of transportation for me while in Sarajevo.