Epic Games released Unreal Engine 4 at GDC two years ago, and removed its subscription fee at the next year's show. This year, one of the things that they will show is Unreal Editor in VR with the HTC Vive. Using the system's motion controllers, you will be able to move objects and access UI panels in the virtual environment. They open the video declaring that this is not an experimental project.
Without using this technology, it's hard to comment on its usability. It definitely looks interesting, and might be useful for VR experiences. You can see what your experience will look like as you create it, and you probably even save a bit of time in rapid iteration by not continuously wearing and removing the equipment. I wonder how precise it will be though, since the laser pointers and objects seemed to snap and jitter a bit. That said, it might be just as precise and, even still, it only really matters how it looks and behaves, and it shouldn't even prevent minor tweaks after the fact anyway.
Epic Games expects to discuss the release plans at the show.