His voice and singing have, imho, improved with age.

I came to his music kinda backwards. I discovered his poetry before I understood he was a song writer, when a beloved teacher/mentor died and I stumbled across his poem, "There Are Some Men." I was such a hick I didn't know he also wrote songs. Not long afterward I was listening to Judy Collins sing his songs, but wasn't one to pay attention to who wrote the songs on an album. It was 2 or 3 years before I finally read the liner notes.