Take for example software development. It has huge potential to improve how efficiently we can work together remotely. It is often difficult to communicate very well with remote team members, and to develop a rapport with them. But imagine if you could be pair programming right beside them, in a VR setting, pointing to some code in a floating IDE or something, and explaining to them how it works. Or you could pull up a virtual "white board" and start drawing maybe.
It could also go a long way to making work more comfortable. With your computer being just a VR headset, it would be easy to work in a laid back recliner, standing in your office, or even lying down.
In AR, the graphics don't have to be as good. Text and line drawing alone would be useful. This translates to less-clunky headgear. The Microsoft HoloLens is far less clunky than the HTC Vibe or Oculus Rift. Being able to walk an oil refinery or a server farm or a WalMart and have displays of what everything was and how it was doing would be valuable.
Personally I think that features like virtual workspaces (e.g. multi-monitor displays / overlays) and HUDs (e.g. vehicle navigation) are going to be game-changing outside of the entertainment industry, when the headset tech gets to where it needs to be; this will probably be better implemented as an AR overlay (a la Hololens) than full VR.