Seems to me, this topic has been addressed on an earlier thread. My gut reaction when learning that Mayer was into the Dead was a kinda snarky, "now I can attend a show with my daughters" reaction. I tell you what, my attitude has changed. Youtube his take on Althea that he played at Red Rocks a couple years ago. Damn good in my opinion. Watching him interview Weir as the late show host, the guy's funny and to me, seems to have a genuine love and admiration for the music. More power to him.
Anything that moves any part of the music industry away from the formulaic horse-shit it has served to the masses for 20+ years is just-alright in my book. If a few kids get to understand and enjoy live music and improvisation...so much the better.
Just another old-fart opinion.