In Blueprint - SOLAR01 has anyone populated the Master Data and Organizational Units?
What purpose does it serve and what are the benefits?
Purpose is during blueprinting you are determing your business processes as they will be designed for the "to be" for whatever SAP solution you are implementing. In order to define your business processes you need to have master data and org unit elements. Within the BPR (business process repository) depending on roadmap/flavor as well as the solution you are trying to implement, there are predefined master data elements and org units that are delivered. The benefit is there are some predifined for SAP solutions within the BPR.
Another way to think of it is in terms of defining your scope, which is basically what you're doing in SOLAR01... defining the scope of your project. The Master Data and Org Unit sections allow you to define the Master Data and Org Units that will be used by in the Business Scenarios that you define.
Note that you can define both the Master Data and Org Units at two different levels: 1) project level, or 2) scenario level. Which level you define them at depends upon whether or not you want the data objects to apply globally (to the entire project) or locally (to only one or a few business scenarios within the project).
In terms of benefits, Michael basically covers it in his response. By pulling standard Master Data and Org Unit objects into your Blueprint, you also get the associated transactions used for managing those objects.
Thanks folks greatly appreciate.