I've ridden them all over the world. How good or miserable they are depends upon the ethnic composition of the city. In Germany & Japan they're great, those in China are pretty good too. London and Paris will get you there without too much fuss but you have to watch for pickpockets. In most U.S. cities you're taking your life into your own hands by getting on them, they're full of gangs and drug addicts.
In many other countries the middle class relies upon public transportation such as subways and trains. In the U.S. public transportation is the realm of the underclass for the most part, people that can afford it will take their own cars with the exception of some super dense places like NYC, Boston or D.C.
