I'm more of a rock drummer, yet I've started to take up the guitar too.
For the last two years, I did a GCSE in Music. Listening and appraisal was a big part of that, with the final exam being based on that and worth 40% of the final marks. I ended up with a very high A (1-2% off an A*), but my main downfall was in composing. I made three compositions, a remix of Pretty Fly for a White Guy, a drum rondo and a minimalist piece for guitar, piano and drum kit. I got consistent marks in all of these (about 23/30, with the A* threshold at around 27.)
So, I have the ability to make music, but I just need a drive. Also, I think one of my main weak points is writing a decent melody, which is natural for someone whose first instrument was the drum kit...