the SPAC is the greatest! I've seen DMB there a few times (maybe 5 times), the Allman Brothers (my bro and I almost got arrested), and The Dead (featuring Warren Haynes - they closed with
Layla, it was awesome!).
I havent seen concerts at too many places but I absolutely love the SPAC. Its the greatest place to tailgate and the venue is SPACtacular!
http://www.youtube.com/watch?v=D2sfelvHAlU (could only find the Eric Clapton version)