I had the pleasure of meeting and chatting with him (and Pat Sansone and John Stirratt) at last year's Solid Sound Festival. I'm 6ft tall and Nels was taller than me; my guess is 6'3". FTR he's as nice in person as he was in this video. Very approachable, easy to talk to.
Pat Sansone was equally amazing to talk to, even more engaging. He took my band's EP as well!