I had never hear of Warren Haynes either, thanks for introducing me to him. I will listen to more of him also.
I recommend checking out his cover of Cortez the Killer with DMB:
He's got some real history as a musical road warrior and serious stage presence. He released a CD maybe in 2002 where he did a bunch of songs and covers live from Bonoroo... It was pretty good because he covered U2's "One" and did a few other songs like "The Real Thing"... Playing in Govt Mule, he also rocked a lot, but there's a distinct difference in Govt Mule music and his cover versions of other music. I almost feel like he puts more soul into the covers because he has to be better than the original.