Prior to reading the book \ sitting the exam I had developed a few relatively basic SSIS packages, but as a production DBA supporting our Data warehouse I regularly investigate issues with SSIS packages developed by others.
I would say that you need a decent understanding of data warehouse design in order to really get the most out of the book. But everything you need to know for the exam is in there.
It was the only resource I used to study for the exam.
MCITP SQL 2005, MCSA SQL 2012