A massive +1.
He truly is one of the few who really transcends the guitar. It's simply amazing music, regardless of instrument/tuning.
L'Alchimiste, Chant de Nuit, Silent Passenger, J'ardin Adonis, So Long Michael, and many more, are aboslute MUST-listens for any acoustic guitarist. In fact, just buy the album Intuite, and then buy Altiplanos
Jimmy Page used DADGAD on "Blackmountainside" - which he ripped off from Bert Jansch, who did use DADGAD occasionally, but not (AFAIK) on his original "Blackwaterside".
But Jansch is an essential influence for all fingerstylists to check out. Here's his Blackwaterside (open D I think): http://www.youtube.com/watch?v=Yp-CkH56G34&feature=related