[andrewla]

It does not (directly) allow multiple simultaneous streams. It allows multiple simultaneous users. This means setting up a dummy google account for each device that you wish to have play simultaneously, which is a bit of a pain.

Ideally it would be more Netflix-style, which puts a limit on the number of devices but does not really care about "identity", though obviously sharing the password to your Google account is a non-starter for family sharing cases.