I've been playing for a very long time now, i started when i was about 4ish, and i can read music, however, i hardly ever do, it's to much of a hassle, i prefer to use TABs if anything, i mainly go by ear, reading music isn't all that important unless you want to be a cover player for the rest of your life. I know my band always work songs out in jams, i , or one of the others come in with an idea and we build on it, i don't hand out sheet music and say "play this!" thats not what a band is meant to be.
And those who say you can't be a good musician without knowing how to read sheet music, take a look at an aussie guitar player named Tommy emmanuel, never read a note of music in his life and yet he is one of the best guitarist in the world, even chet atkins thinks so and you can't get better the chet! And does BB king read music? he's a mainly improv kinda guy.
I agree that it can be extremely helpful, but i don't think it's crucial (spellin)
p.s i doubt stevey wonder reads music