I'll bet they didn't show this 12" screen running any of the legacy windows apps
What do people generally buy tablets for? In my view tablets are best for consuming content, with about 5% input done through keyboard. Except for watching movies, or for super exotic porn watching, 12" is a horrible form factor.
About half the Android tablets I've seen are used for dual purposes - making phone calls, as well as viewing mails, videos, Whatsapp and what not. A 12" tablet for making calls would make as much sense as navigating a 17" screen using touch or keyboard, but no mouse.
Content creation is best done on a laptop or ideally, on a desktop. So a 12" portable device is neither good for consuming content, making phone calls or creating content. So who is the target user for the Surface Pro 3?