D.C. Tardy has another really great post on ConfigMgr Hierachy.
Here is a snippet:
You are planning to install a Configuration Manager 2012 environment within your organization? That is great news. If you are like most organizations, you already have an earlier version of Configuration Manager in your enterprise. Given that, I wanted to take the time to explain some important changes in the hierarchy design. (For those that don’t have an earlier version, we have great documentation to help you plan your hierarchy from scratch at Getting Started with System Center 2012 Configuration Manager).
Configuration Manager 2012 infrastructure requirements are dramatically different than previous versions. There is much less infrastructure involved in a Configuration Manager 2012 implementation, which is great! But it does require changing how you approach hierarchy design. The good news is that you don’t need to throw out your old designs and your requirements won’t vary greatly. It is how you satisfy those requirements that will change.
Here are some great links he provided in his post: