I went to Bucharest last year. A little rough around the edges (part of its charm!), but an absolutely fascinating city. Try and have a ride on the Metro. The stations are rather grim, but thats why I liked it! The Metro does have some interesting architecture, such as at Piata Victoriei. They have some really modern and clean rolling stock, but also look out for the older Romanian-built Astra IVA trains on the M4 line.
The buses are literally all white Mercedes-Benz Citaros, so not particularly interesting. But there are trolleybuses, which I always find fascinating. I can't remember their routes, but I took photos of a few around Universitate (University). The trams I saw look ancient and were covered in graffiti, but sadly I did not have time for a ride. Be aware that tickets between tram/bus and the Metro are completely seperate, which is rather frustrating (although I think they are trying to change this). It seems you have to buy bus/tram tickets from ticket booths, which I couldn't find. In the end, it seemed too much hassle (I was there for just 2 days), so I just concentrated on seeing the actual sights of the city, and the Metro and the rail stations.
Visiting Gara du Nord (North Station) is a must! The architecture is stunning. And you can see some very ancient rolling stock! Just keep your wits about you around the main station though, as is often the case at many European main stations.
Transport aside, the city has some great architecture (they stuff that wasn't bombed or demolished by the former dictator). Try to see the Old Town, which gives you an impression of what the whole city would have been like - known as the 'Paris of the East' before it was bombed. I went in a few cafes, which were like going in a high-end Paris cafe, but were still cheaper than what a McDonalds would cost in Paris. Depends on how much time you have of course!
