In Oregon, it's currently illegal to talk while driving without a hands-free device.
Despite this, when I'm at the front of the line at a red light, waiting to turn left, I see lots of people on the phone, holding it up to their head. I see people on phones driving (usually speeding) through residential streets. I see people staring down at their phone at a red light after it's just turned green and they're still not moving yet. On the highway I see people driving slower than the speed limit and when I pass them - yup, they're on a phone. I see people in grocery store parking lots doing strange things, blasting through crosswalks and stop signs in front of kids instead of stopping (even with kids of their own in the back of their car). Basically, it's really easy to spot people on phones while they're driving because they're driving badly in an obvious way, and there are a lot of them around, despite it being illegal.
OK, so we get everybody a hands-free device and.....well, actually, no. There's a bunch of research that shows that it's the talking that causes the tunnel-vision and slowness, not the fact that you're holding a phone. So hands-free devices don't actually help, even though the law sort of implies that they do.
Personally, I won't talk on a phone while driving, and if I find myself on the phone with someone who is driving, I politely ask them to call back when they're done driving and hang up.
In theory, talking to passengers is OK because they can stop talking when traffic is tricky, but in practice I've missed exits while talking to passengers (I'm sure you have too).
So that's the baseline on my view of phone use while driving, so you understand where I'm coming from.
When I'm driving and have my phone in my pocket, I get emails and texts and the phone beeps and I ignore it.
When I'm driving and have Glass on my head, I get emails and texts and glass beeps and I ignore it.
When I have Glass on my head, it does slightly block my view of the ceiling of my vehicle, but not anything out any window. If the display somehow ended up between my eye and the road, it's transparent, so I can see through it - but it's not in the way, it's up on the ceiling.
I do have a GPS that sits on on the dash. I find the audio reminders to turn to be very useful, and sometimes the map showing the lanes is useful to glance at to figure out which lane I need to be in. The rest of the time, the moving map actually draws my eye to it instead of the road, and the audio is kind of annoying to non-drivers or kids sleeping in the back of the car.
I've used the GPS in Glass while driving - it is *way less distracting* than my on-dash gps - the dings are very clear, the audio directions are great, and the screen *shuts off entirely* while on the straightaway. You can't view texts or emails while in gps mode, at most you can turn on the map again by tilting your head. When you're near a turn, the screen turns back on, you can glance at which lane you need to be in, just like you'd glance at the GPS on the dash, and you make your turn.
Lately I've also seen a rash of drivers trying to make the exit after they've just missed it - they end up on the left shoulder of the exit, narrowly missing the concrete at the diagonal intersection. I'm not sure what's going on with them (I'd guess they're on the phone, too and are panicking about missing the exit), but a GPS to either warn them that the exit is coming up, or allow them to relax and find their way again after the next exit is way less dangerous than making their own new lane, and Glass is the least intrusive best GPS I've ever used.