While "displays" have the connotation of affording visual output, "surfaces" invite the users to interact. What happens then when the surfaces are also displays, when a direct input interface space and output visual space are superimposed onto the same touch interactive surfaces? In the past three years at MERL, we have systematically examined, studied and evaluated, holistically, user interface and interaction techniques on one particular type of direct-touch computational surfaces - multi-touch multi-user tabletops. We have created and prototyped a set of novel interface systems ranging from a photo storysharing table called PDH (Personal Digital Historian) to the DiamondSpin tabletop tool kit, and UbiTable, to interaction concepts including CoRDs, Modal Spaces, Glimpse multi-level input model, ExpressiveTouch bimanual gestures and bifocal tabletop display interactions. We have also obtained preliminary findings on non-speech audio feedback on multi-user interactive tabletops, and some of the effects of the size of tables and size of groups on different aspects of multi-user collaboration. Our future research will investigate interaction and visualization across tablecentric interactive spaces with multiple surfaces of tabletops and walls in a new project called DiamondSpace.