The whole point of the device is to provide a room-level AR experience and it will be a game changer when it reaches a certain point. We'll see how close it gets for the first gen, but I imagine it will at least satisfy enthusiasts and those that need a headset for their job. Even the second generation will probably just target budget enthusiasts. I imagine it will take to at least the 3rd or 4th generation before it gets more mainstream, but it is hard to predict these things. It isn't going to support leaving the house, but no device in this class will support that. This is like a MacBook Pro. You are not going to use that while walking down the street either. It will be for professional visualizations, modeling/art, working with a large virtual desktop, games (diorama-like holograms or full immersion), light-field movies, AR "websites", watching traditional movies/games on a large virtual screen, etc. This is probably the first headset where text will be clear enough that it can start to be useful for more than previous headsets could pull off.
It will never give you turn-by-turn directions while going down a street. Apple will probably make that later "Apple Glass" device, but it will be very limited due to its form-factor. I imagine such a device in its first generations will likely be very low resolution to support a thin and light device. In other words, you might get arrows and breadcrumb trails in maps, but you will need to look at the paired device to read most text since the display just won't be capable of more then blurry text. I doubt you would be able to play more than simple games and nothing would look realistic. Apple headset will be like the Holodeck, while Apple Glass will be Star Wars holograms all the way.