miscellaneous other reference material, blogs, and videos (see the GPA Home Page for a full list)
Is this sufficient? If not, what else would you like to see that would make your use of GPA more successful?
Examples that have been discussed are in-depth videos showing how to use the product, white papers on various topics related to GPA, and anything else that would help you be more effective and productive in using the product.
By the way, we're also started creating Knowledge Base articles for the product, which includes various GPA "Tips & Tricks" to help enhance your use of the product.
Note that the Quick Start Guide is going to be the starting point for most users; after you've had a chance to go through this document, start playing with the tool, and then refer to the help file for detailed information. The Knowledge Base articles are highly-focused on a particular topic, and are probably best viewed by skimming the titles and see if one or more of the articles applies to your particular situation.
Also, there are a number of introductory videos and other information available from the GPA Home Page. It should be self-evident from most titles what particular level of user would benefit most from each specific article.