This technology has been available in Cadillacs for years. Go drive an ATS if you want to see it in action. Not distracting at all.
ATS HUD: http://www.youtube.com/watch?v=tpXYwoZ6zWw
For a while they even had a radar overlay so you could see deer in the road on your HUD before your eyes could in the dark.
Looks like the Cadillac HUD is fairly low on the windshield:
http://cdn0.mos.techradar.futurecdn.net//art/car%20tech/Head...
Ideally, this should be tested.