Cool location setup I've seen is one of the trays (like the Gitzo G065 or Manfrotto 183) + the laptop sleeve from a Lowepro CompuPrimus AW (picture). Little bit of jiggery pokery to get the tray into the base of the lowepro case + cutting a hole to allow you to attach your quick release mount of choice to the bottom of the tray, and hot diggity it's a slick system. Saw a digi-assistant with that setup and I was waaay jealous. Grab a HyperMac for extra juice and hang it from the tripod as weight to make it more stable. Niiiiice
Unfortunately I don't think they sell the laptop sleeve from the CompuPrimus seperately, because I really want one!!