UML is based on OMT, Booch, OOSE and other important modeling language available. You will have little trouble getting to work with UML if you have been trained on these three languages.
UML does not guarantee project success but it does improve many things. It significantly lowers the perpetual cost of training and retooling when changing between projects or organizations. It provides the opportunity for new integration between tools, processes, and domains.
UML is semantically more expressive than traditional ER techniques. Not only can you model same elements as you can with ER techniques, you can model other kinds of relationships as well as behavioral characteristics.