I've just followed the instructions for the hello world sample for the SharePoint Framework Preview and I'm getting the error in the title when attempting to run the workbench on my sharepoint dev site.
I get a page that says "Sorry, something went wrong" and then
"The requested operation is part of an experimental feature that is not supported in the current environment."
I've followed the instructions here to set the environment up:
It's step 6 in these instructions that I'm having trouble with: https://github.com/SharePoint/sp-dev-docs/wiki/HelloWorld-WebPart
Any thoughts greatly received.