Docker is a way of making config management easy. Here there really is less stuff. You build a binary with your whole application and all its dependencies that actually self hosts. And is smaller than Docker's init process.
And a VM is better isolated than a Linux container.
EDIT: the restrictions are not necessarily permanent either. Its only a first early release...
Yes, tiny resource overhead while still providing near-complete isolation is a big benefit. The current memory overhead from using file system drivers and TCP/IP networking is around 8MB, and I'm sure there's a bunch of fat in there that could be trimmed off.
It's going to be interesting to see where the exact set of supported application images converges as use cases arise. For example, I'm pretty sure fork() will never be supported -- would it fork the VM? -- but some of the other things are up for discussion.
And a VM is better isolated than a Linux container.
EDIT: the restrictions are not necessarily permanent either. Its only a first early release...