I think its pretty easy to differentiate between major and minor, they have very different sounds. Meter, however, has always been a problem for me. Like I can tell the difference between 4/4 and 3/4, but not between like 2/4, and 4/4. I actually don't thinik that is neccesary, but like the person above me said, its pretty easy to tell if the music is in duple or triple meter.