For me, not so much. Although it seems like something that I expected to encounter in the future, I can't really find a use case for myself. I'm curious, what potential functionality most excites you?
Also, imagine walking around Boston or New York and having historic sites described to you audibly while an overlay of the way it used to look was displayed.
Definitely the bikes GPS/Odometer! People pay hundreds for dedicated bike GPSs (see, Garmin Edge series). Since I'm no racer, I could never bring myself to buy anything like that. I just use Strava on my phone. Sure, a smartphone with GPS would work fine, but this bring's the best of a dedicated GPS all over! You can see a small 'mini-map' anytime you want. You can see anything the Garmin would show you. I only hope this gets optimized real well! Gosh I love bikes.
Aside from what has been demoed, the api looks super easy to work with. It looks mostly to be just pushing json to google. I can create notifications that get pushed out of the way in my vision. I guess my main excitement is that it's a friggin screen in your face at all times.