Jon, I've seen the Pogues at their height & they were fantastic. I've also seen Shane McGowan when he was incoherently drunk, and hopelessly depressingly pathetic - which made me very sad for him (though he was probably quite happy...).
He surely must count as a professional (since its his profession) - but he was certainly short-changing his audience that day. (It was a festival though, so didn't have that bad an impact, to be fair).
It must be quite rare for a professional to stay in the profession if they are regularly in that state. With Shane I suppose it is part of the mystique - but then I felt bad for buying into that.
Kris
PS. B*ggered if I know what my point is....