Hamlet at New World Notes is pointing out David Rowe has a SL VR Viewer working. The page Hamlet linked to is out of date. The new news is in the comments where David says,

David Rowe Post author5 Jul 2016 at 11:22 am
Just tried LL’s Rift viewer and, well, it’s surprisingly un-good. It’s like the graphics are being fed from the wrong framebuffer object or the pipeline is being misconfigured when you switch into HMD view. Intentional or bugs? I suppose time will tell. The graphics should be able to be so much better (even if understandably the FPS isn’t so good)!
Links:
Note Jo Yardley’s comment about being able to use Vorpx with a regular viewer (i,e., like Firestorm, Alchemy, or LL’s regular viewer) to view Second Life in your Rift. I haven’t tried it myself but am told it can be used.

