Multisite Network

Hello,

This seems like a great plugin! Very useful for creating communities with various access levels.
Before using it though I have one question. When installing it for a multisite network, is it possible to do user management for the entire network or is it only site by site?
To be more precise, can I create groups (and sub-groups) that will be applied to all the sites in the network?

Hope the question is clear enough.
Thanks.