Pretty sure you can't read your email or browse your newsfeed on a BMW's HUD.
Now, if release Glass have some way of ensuring that you can't do things that are unarguably distracting and irrelevant to the task at hand while driving, then sure, it seems like an improvement on the standard way of using GPS or taking calls. And from the stories I read, Google does have a point: "Glass is still in beta, so don't rush judgement."
It certainly comes off more like typical corporate concern for the bottom line though.