Confusion about the purpose of dev containers

So it looks like the problem is that on first run, with several other project windows open, Webstorm never got around to closing my application window and re-opening it in the container connection. 

For a feature that's described entirely without screenshot in the documentation, that's pretty poor DX. With pictures I would notice the distinctions between the dev container UI and the existing UI.

(Also why not offer to copy my .idea files into the container so I have my run configs at hand?)

Hello, Jdmarshall. 

For now, the dev containers feature uses Remote Development under the hood. With it, there is little difference between the local IDE UI and the UI of the IDE running inside the dev container. The major ones you can notice are the Backend Status Details widget on the left of the Project widget (see the screenshot below) and the Settings | Advanced Settings categories marked as Host and Client.

(Also why not offer to copy my .idea files into the container so I have my run configs at hand?)

If you use the Mount Sources or From Local Project option, your project is copied inside the dev container automatically. If you use the Clone Sources or From VCS Project option, the VCS project is cloned inside the dev container, and it is implied that it already has all the necessary data (including Run configurations) committed into the VCS.

So it looks like the problem is that on first run, with several other project windows open, Webstorm never got around to closing my application window and re-opening it in the container connection. 

Could you please collect (Help | Collect Logs and Diagnostic Data) and share your IDE logs? I want to check if any relevant exceptions or errors are reported there. To share the logs, please use our JetBrains Uploads service and write the ID you receive there.