In a sense, I have a HUD. Over the years, I've found it invaluable. It's a good, old-fashioned GPS with a sucker-mount. My job involves a lot of driving on unfamiliar two-lane highways in rural Ontario. I keep my GPS mounted just below eye level to the left. It gives me my speed, the shape of the road just ahead, and it will pop up an actual point-of-view picture of some exits and entrances from larger highways. This is available to me without having to take my eyes off the road even for a split second.
It has saved me from at least a couple of accidents (probably minor, but you never know) and allowed me to concentrate on driving rather than trying to spot the appropriate turn-off. These often aren't marked at all, or have a sign the size of a banker's conscience...great for reading as you miss it on the way past.
That said, even just shifting my concentration from the road to the GPS and back did require a little learning. The most important (and safest) thing, though, is that my eyes are never entirely off the road ahead. In addition to keeping me safely on a road that may take some unexpected turns, this has certainly saved the lives of a large number of apparently suicide-prone wildlife and domestic animals. On a purely practical level, anyone who has ever hit something the size of a deer knows it's no laughing matter. Two of those idiotic creatures are alive today thanks to my "HUD". And so am I.