You will find the principles as well as the technical implementation of the connector.
Basically, the main use cases served after the connector has been implemented are:
profile synchronization from v7 to ACS
audience synchronization from v7 to ACS
landing page synchronization from v7 to ACS
You can as well ask consulting to configure extra synchronizations in case you need more data.
Once you have your v7 data in ACS, the main benefits are that you can leverage the improved UI of ACS to design emails and workflows. You will also benefit from the ACS MTA which has higher capacity in terms of throughput (because more recent mainly). You will also be able to use the ACS dynamic reports, etc.
Let me know if you need more details on a specific use case or feature,