The EPM 2007 Test Data Population Tool solution starter was published on CodePlex today: http://www.codeplex.com/EPMDatapop
So if you need to get some sample data loaded up for testing purposes - this is the tool for you! Documentation and source code is also posted so this will also be a good tool for learning how the PSI is used for getting data into the server.
Q & A is posted in the discussion area - but I'll repeat this one here...
Q: Is the tool supported?
A: There is no support in terms of CSS/PSS. We expect the support being a CodePlex community effort. Please note that the customization code uses standard supported web service calls available out of the box in EPM2007.