When I was playing music, I could never really sightread, but, based on what I could do in the way of mimmicing, if I heard it once, I could usually play it, well, then its not really sightreading is it? But most guys I knew played too straight, by the book, playing exactly what was written, not able to "swing" or inflect style or play what the writer wanted played or how it was played by others. I could never sit down and write out what I heard, but given sheet music and hearing it, I found I could play it no problem the way it was meant to be played.