The server side is currently relaying messages for the in-progress iOS and Chromium clients. That's functionality that exists today, even though the clients are still under development. The TextSecure server is an elegant and important part of TextSecure's infrastructure. I stand by my assertion that it's an oversimplification to say that TextSecure == Google's Servers.

Google does not have access to any metadata, other than the fact that you are a TextSecure user who has received a Push notification. GCM payloads are fully encrypted. Google cannot tell who a message was from, they cannot see which numbers were involved (users are free to register with a number that is different than the one assigned to the cell phone that is running TextSecure), they cannot tell whether or not it was part of a group conversation, and they cannot see its contents.