I've got my 'unofficial' grade 7 in piano. I say unofficial because I didn't bother to take any of the conservatory tests, but I was playing at the grade 7 level. Grade 3 (probably 2) theory level too I think.

I don't think it'll ever be directly useful for me, nor will any of the other instruments my parents crammed down my throat, but it's like a general arts degree - opens your eyes to seeing more and being open minded to learning other concepts then you normally wouldn't.