Details just went up at http://www.microsoft.com/surface/en/us/whatissurface.aspx

Product website:
http://surface.com

Briefly from today’s presentation: 

• It is a Windows 8 Tablet, sold directly by Microsoft and branded as “Surface”
• 10.6 inch 16:9 aspect ratio
• Proprietary magnesium case with built-in stand
• Magnet cover with built-in multi-touch keyboard
• Two lines:
  • Windows 8 RT ARM processor
  • Windows 8 Pro based on Intel chips
• Comes with Office
• Supports stylus
• 600 DPI screen
• Pricing not announced. Likely to be in same range as Ultrabooks