@wim, you’re right that it isn’t currently in the menu. The original RhinoCycles.rhp is now a utility plug-in, meaning that at the moment Cycles is available only through the viewport as a mode. It should be available as the mode Raytraced, but I have seen also that it still is under the old name Rendered with Cycles. This is done in preparation for v6, where Cycles won’t be directly available as a renderer, rather there will be a separate plug-in that enables the old behavior. I intended to make a post about that already two weeks ago, but apparently that intention never got realized. I apologize for that (perhaps I can play here the I-was-working-really-hard card).
There are three main things I’m currently working on. First I work on preventing crashes when resizing viewport (some mechanism changes made this sometimes crash while rendering into viewport). Once that is done I continue with the so-called shadow catcher node, the second major item. This is necessary for the Shadows Only -ground plane. And the third task is to ensure ViewportCaptureTo* works properly for the Raytraced mode.
I will have a plug-in available in the near future to get the semi-modal rendering (into the separate render window) again, but the above list needs my current attention.
Tips for getting RhinoCycles back as renderer (sooner rather than later): make me happy so code typing efficiency gets boosted. Happiness is fostered through the posting of nice renderings done with RhinoCycles/viewport, good cheering while I frantically type code, and virtual puppy eyes that clearly give the message the plug-in is dearly needed.
/Nathan