Seybold have not shipped over free copies of a guide to IPEX this time which is a great disappointment.
They have announced a PDF Workflow Shootout with results to be announced at Seybold San Fancisco on September 10th. This will involve a survey of 150,000 PDF creators and output service providers. The tests will assume PDFx 1a so this is some sort of standard unless the test results are alarming.
There is a free article on their website. Not quite the same as a hard copy guide to IPEX but an intriduction to the issues raised by the PDF Workflow shootout.