I was going back and forth for a long time on whether or not to learn Esperanto. What finally convinced me was this Ted Talk.
Esperanto is definitely not perfect, but since it's so much easier to learn than any natural language, that by itself, makes it worthwhile. Assuming Esperanto can be learned ten times faster than a natural language, that means that one year of study of Esperanto would give you the proficiency of ten years of study of a natural language. Also, since a knowledge of Esperanto has been shown to greatly help people acquire additional languages more easily, I think that makes it a worthwhile language for people to study.