I certainly find it a lot easier to play the melody when I have the music in front of me, so having at least some ability to read music is important for me; On the other hand, I visited someone last week who plays piano wonderfully well and can't read a single note. I don't understand it, either, but some people seem to be made that way! A friend of mine plays guitar and is also quite incapable of reading music. Seems to me it's not a necessity for everyone, but it's a great help for most of us!