I think HoloLens would be great for something like seeing how furniture would look re-arranged (without actually moving it) or virtually redecorating but these probably aren't mainstream. What mainstream things will you do, in your home, with your home visible and things laid over top. With no controller device other than what the devices detects your hands doing.
Having the equivalent of a 100" TV playing video on your wall while you have the equivalent of a weightless 20" tablet that you can drag into view of out of view whenever you want while you have a Skype video call with friends or relatives pinned to a corner while you casually play Bejeweled (or whatever game is a big hit with casual PC gamer's now days) while a stock ticker does it's thing but you have set up custom points where it notifies you when the stock hits certain points while you edit a shopping list from input gotten from the Skype video call while you coordinate plans for the wedding while you play with your dog or cat while you watch your children to make sure they don't get in trouble (in the real world) while you get ready for a night out on the town while you change your babies diaper while you clean up the living room to get ready for guests while you re-arrange the furniture in the room for the X-th time because your spouse is tired of the current look while you install a new video card into your PC while you assemble the doll house you just got for your daughter while you...
Obviously not all of that at once, but you'd certainly be able to do many of those things simultaneously. VR would fail here as you wouldn't be able to do many of those while simultaneously interacting with and/or monitoring what's going on in the real world.
Sure you can do all that with a tablet and expensive TV and a PC and... But the potential is there to do many/all of those things on once device. Sort of like, yes, you can still get up off the couch and change channels and volume on your TV manually, but why do that when you have a remote? And sure you can have a remote for every device in your home entertainment system (receiver, BluRay player, TV, cable box, DVR, etc.), but why do that when you can have one remote that controls all of them?
That's what I could think of. Which probably isn't even a fraction of what some developers out there could potentially think of.
Hell you could have a Skype call with someone while changing the oil in your car and take notes without getting the oil all over your tablet. Or have a Skype call with your physician to take a look at your baby to see if you actually need to come in for a visit because your baby made a strange noise. Since, the physician would be able to see everything that you see and hear what you hear. Which would apply to veterinarians and pets, cars and mechanics, food and cooks, the sky is the limit. Sure a tablet is nice to pull up recipes for cooking, but what if the recipe was in view the entire time you're cooking dinner?
Hell for me, I could have someone I know help me pick out clothes (I'm red-green color blind) that actually match without them actually being there.
The possibilities are endless. Sure you can do a lot of the things with a combination of devices. But then modern life is full of things that let you consolidate actions into once device. After all, wasn't that the attraction of the PC? And tablets? And smartphones? This has the potential to move all of that onto one device.
Yes, there are still many challenges and hurdles to overcome before it's something that is intuitive to use and offers robust controls for many of the above mentioned tasks. But you only asked about the possibilities of AR. It's up to Microsoft and the developers (and any other company that is trying to do AR) to come up with solutions to some very real problems.
Hell, a potentially very interesting thing would be some form of OCR with auto-translate abilities could allow you to read a foreign book/newspaper/pamphlet/menu in your language (to some degree) with it automatically replacing the words in the book/newspaper/pamphlet/menu with words in your language (you'd never see the foreign text unless you instructed the device to stop auto-translation).
Regards,
SB