I still have problems with notation, but learning music theory is very helpful to me. I began playing by ear, so I do best by ear training. For example, while it may be good to learn a certain triad, I have to both learn the triad, then hear it. It helps me distinguish between different chords, so that I can write down what I come up with. As my knowledge of music thory gets better, I'm better able to write down what I come up with, because I have a rough idea of the chords (for example, I could identify a certain passage as a major seventh, and identify the root note). Notation is becoming easier with practice. The theory's taking quite a while, but I feel that it's worth it.