my own experience is that learning functional programming gave me more options - that can be useful when solving problems. when writing code for myself i try to combine the best of function, oo and procedural styles, while staying within "good taste" for the language i am using (sometimes i cannot choose the language).
so yes it's worth it, but your question leans too much to extremes: it's not a silver bullet any more than oo was; it's a mental tool that does help in every-day programming.
Functional programming is not always the optimal choice. But when it is, it is awesome.