Thanks dudes, I love Slashdot! So relevant and helpful!
There is almost no difference between say a $250 helmet and a $1000 helmet other than the graphics.
Sure, the super-cheap $50-$80 helmets can be seriously lacking in safety but almost anything above that is fine if it fits your head and has the features you want (fit, noise, venting, etc).
Worth it? Meh, probably not.
I wonder how much it would cost to simply take a regular helmet and some Chinese electronics off eBay to make the same thing. I'm guessing significantly less even including your time to build it.
I mean you're looking at less than $100 in raw parts for GPS + Arduino + HD Camera + display controller/OSD. Not sure about the HUD part but I believe it's just a projection on a small piece of glass, probably also less than $100 in parts by itself not to mention alternative hardware implementations that might be cheaper. Add $300 for a decent helmet, wire it up and you're done.
Personally I think I would find the HUD hardware incredibly distracting. Not the HUD itself mind you, but the stalk that sticks up in front of your eye. I would rather it be projected on the visor even if that means it's not always available (eg. when the visor is up).