I listen to it so much that I find myself singing it to myself on the way to work, and at inopportune moments. In fact, "Do I find myself singing this one to myself on the way to work, and at inopportune moments?" is a key question for me in terms of whether I add a song to my repertoire. To be honest, I never really set out to "learn a song" -- it's the ones that get under my skin that I'm interested in.

I'd echo what Rumncoke says about accompaniment though -- I'd want to be able to sing it unaccompanied before I decided whether to pick up my guitar or concertina.