Windows 7 is a landmark product for Microsoft with support for things like sensors and multitouch. With just months (which quickly turned into weeks) to go until the show, it was decided that the best way to accelerate getting the hardware to support these new features in the hands of the developers would be to gift them a laptop at PDC. The problem was that there wasn't a retail laptop available that supported everything we wanted you to have, especially in a price point that would allow us to give out thousands of them.
I'm happy to say I'm typing this up on one now, and it's an incredible machine. Built upon the Acer Aspire 1420P chassis, this convertible TabletPC has a Core2 Duo U2300 processor, Mobile Intel GS45 video, 2GB of DDR3 1066 MHz memory (supports up to 8GB), an 11.6" 1366x768 multitouch screen, webcam/mic, 3G WWAN, WLAN (supporting up to Draft-N), S/PDIF for digital speakers, 3 USB, 250GB HDD, card reader, and even an HDMI port.
In addition we had some other custom things added including a built-in accelerometer. You might notice this when you rotate the tablet and the screen stays oriented. All the hotkeys are supported through BIOS and firmware, there is a button for Flip-3D
(cool!), and WWAN is supported by the WWAN stack built in to Windows 7.
In addition you've got Corel Paint It! Touch, Office 2010 (pre-beta), Windows XP Mode and Virtual PC, Microsoft Touch Pack, and the Windows Live Suite. This is a custom PC built on an unreleased (as of yet) machine, you can't get it anywhere else.
So PDC developers, go forth and populate the planet with awesome software. And please, if you make something cool - let us know.
Update: A couple things I forgot to mention. The PDC Laptop has HDMI AND a VGA out, as well as bluetooth. You might notice on the flight home that the battery life can be nearly 8 hours. And a tip for browsing the web while in Tablet configuration, you can hold it on each side and use your thumbs to alternate flicking the page up and down or both at once to resize with multitouch.