Yes!!!
I have the Developer version of this awesome piece of tech, and so far am loving it. I have successfully gotten it to work in SL, both on Windows and Mac- however I hope to see MUCH more development from CtrlAltStudio on the Mac side of things (since that's what I use predominately).
Wearing the VR gear makes for an entirely new experience InWorld, as it really feels like you are In the World. The dev version is pretty low-res, so I'm currently debating on making new signage, or just wait till the consumer version comes out, which is supposed to have something like 4000 px, rather than 1200x800 (ish). Currently, looking at things up close definitely gives that "screen door" effect, but I can look past that.
I am (throughout this month) building our an Island SIM geard toward RIFTers. So far what I've got is pretty basic, but just walking on one of my floating pathways with the Rift is really cool. You can look down over the edge and see the water waaay below.. I am a happy neko, indeed.