I've got about 6 months to a year of working with AWS in an enterprise environment, specifically one rather large scale deployment alongside a consultant. I've been in IT for about 9 years as a sysadmin. Then got let go from my job unexpectedly 2 weeks ago.
I started on the LA CSAA course the next day. After completing it, I read the individual service FAQs but struggled with the whitepapers -- just too dry.
The best prep though was Thomas Haslett's own blog post here:
The day-of mindset prep and spending the 5 minutes to sketch out a VPC network diagram really helped on quite a few sections.
The quick bit on STS in the course seemed inadequate, as I had 2 or 3 questions on it, as well as a heavy heavy dose of DynamoDB. IAM was covered thoroughly in the test but also in the course, so that seemed adequate.
The questions on the test were definitely a notch or two harder than the practice exam. Typically just more specific about the interconnection between services.