That's what I understand by a "learning curve" too. I would tend to agree with the wikipedia proposed explanation: "steep" is, in some contexts, synonymous with "difficult". Saying "you have to climb a shallow learning curve" would certainly be interpreted wrongly by most people.

Concerning the OP question, I wish I had learnt something interesting at school, instead of the thoroughly irrelevant, utterly boring, mindboggingly wrong pseudoknowledge.

To zedzed and D_Malik: I think what you have in mind is learning to play an instrument as a profession. I that case I agree that the rewards are probably not commensurate to the effort, unless you are exceedingly talented and lucky. But for everybody else it's probably a good idea. If done for its entertainment value it's surely worth it, and it helps you understand and enjoy music at a deeper level. On the minus side, it also makes you realize that most popular music sucks. Really really sucks, to the point of irritating me.