This year I've been using Virtual Desktop. It expects you to put your images in a specific folder in My Pictures, which I find a bit limiting, but it gets the job done and the quality seems high enough.
For the Vive I recommend rendering to 4000x2000 or perhaps 4096x2048. I've done tests in Virtual Desktop as well as custom-developed viewers in Unity with various interpolation methods. It's difficult to notice any improvement above 4000x2000. I'll recommend the same for the Oculus Rift because of earlier experiences in other viewers on the DK2 where 4K was about the maximum you could see without it starting to alias and negligible gains in perceived detail. Future hardware (and perhaps some current hardware) is going to have better resolution so you might consider higher resolutions if you're thinking about future uses, but not for the Vive.
You'll see fewer edge problems in Terragen skies if you render with Defer Atmo/Cloud. Terrain might still have issues. You could render slightly wider and chop off a few pixels as a simpler alternative to painting over the gaps. It's been difficult fixing all edge problems but we should improve this in future builds.
Matt
