Although Microsoft is keeping mum about any official release date for the Surface tabletop touchscreen PC, the software giant has lined up US network operator AT&T as a retail guinea pig – allowing the company to display Surface in several stores.

From 17 April, customers will be able to mess around with Surface at AT&T stores in four US cities, including Atlanta and San Francisco. The bad news is that you won’t be able to buy the interactive table, because the rollout is merely a trial to see how people react to the futuristic device.

Surface, which was codenamed ‘Milan’, is essentially a 30in touchscreen PC mounted into a tabletop. The screen allows users to activate and move items around by touch.

Gadgets can also interact wirelessly with Surface simply by putting them down on the table. For example, you could move pictures from a compact camera and onto Surface just by putting the snapper onto the table.

AT&T’s Surface trial will let customers see graphical overviews of a mobile phone’s features, when they put a handset down on the table. Two handsets can be put on the table and a comparison list of both phones’ features will be displayed. Maps of the US will also be accessible through the in-store Surface demo units.

Microsoft has never given a clear indication of when Surface will be made available. However, last month Microsoft exec Steve Ballmer hinted that mounting consumer demand may see the table made available sooner than the vaguely anticipated 2011 release date.