Has anyone gotten onto this beta yet?
Codespaces makes it easier for developers to onboard to a new company or start contributing to an open-source project. Project maintainers can configure a repository so that, when you create a codespace for the repository, the project's dependencies are included automatically. You can start coding faster by reducing time spent configuring your environment.
I've been on the waiting list for it since they announced Codespaces in May and am still waiting 
In the meantime, I've been exploring VS Code's devcontainer feature, which allows you to configure a docker container for use as a development environment that runs within VS Code. It appears no differently to if you'd opened a project 'normally' in VS Code. When you open a project that has a devcontainer file/ folder, a notification appears asking if you want to run the project within the development container so it's pretty frictionless from a getting started perspective. It looks like GitHub codespaces will use the devcontainer if you've got one.