Dj Shadow is one of my favourite experimental/triphop DJs, and has been integral in shaping the landscape of most electronic music today. Per the previous paragraph as well as common sense, this is not a show to be missed!
After looking at the link on the SMOG Event Page, it looks like tickets are still available at this url: http://www.ticketweb.com/t3/sale/SaleEventDetail?dispatch=loadSelectionData&eventId=3461224&pl=observatory, and are shockingly very cheap. Cancel your plans and GO! Also performing will be Noah D and Pawn.