In a completely surprise move (read: ) at the grand opening of a new Microsoft store in Bellvue, Wash., on Thursday, Dell began lining up buyers for the tab-books, which are expected to the first week of December.

The catch is that the units are only available for pre-order in a Microsoft store--you can't yet pre-order online (though says the Duo will be available online "very soon").

The Dell Inspiron Duo starts at $549 (yes, that's $50 more than the iPad's starting model), and features a swiveling 10.1-inch touch screen, which allows it to be used as both a notebook and a tablet.

The Duo doesn't have the "instant on" capabilities of a conventional tablet--it takes more than half a minute to chug into action from a cold boot--but it does have more muscle, with a 1.5 GHz dual-core Intel 550N Atom processor, 2GB of RAM, a 250GB hard drive, and a Broadcom HD graphics accelerator.

The tablet-notebook has a rubbery chassis and comes in black, blue, and red. It weighs about 3.2lbs, which is pretty average for an ultraportable, though (needless to say) quite heavy for a tablet (Apple's iPad weighs less than half of that, at 1.5lbs). In notebook mode, the Duo runs Windows 7 Home Premium; in tablet mode, it runs Dell's "Stage" mobile user interface.