(This is also a big complaint I have of Google Glass. I don't think I've ever actually seen a single image from Google talking about how it looks from a wearer's point of view.)
http://i.ytimg.com/vi/d-y3bEjEVV8/maxresdefault.jpg
Is the type of pictures I typically see. This is portion of your vision blocked by a semi-transparent area so it can reflect the very small and basic text projection.
When I think of HUD, I think of something that is able to overlay my vision like so:
http://www.niemanlab.org/images/behavio_hud.png (Just first image in google search)
Since neural manipulation or a screen being able to be on a contact lens are probably far away technology wise, that essentially leaves us with having to create something that can either draw or project a screen on a normal pair of glasses.
Once you can wear a prescription or prescription-less pair of fairly normal looking glasses that can draw/display image/shapes/text/color anywhere on the lens, then I think the actual "revolution" will take place and everyone will quickly buy and use them constantly.
Think of it like Siri + CRM + HUD = on demand insights about customer needs, immediate details when a particular problem can be fixed given stock in warehouse. Also this will incredibly strain the user as simply he will have less time to pause between client interactions.
Give it another decade and computer vision will be able to advise technicians that they are about to touch live wire, etc.