LinuxAcademy has been my main resource to prepare the exam. I have also use Qwiklabs (qwiklabs.com) but it only have labs and lacks the videos LA has.
I can't highlight anything especially from the training material but having taking the exam, S3, EC2 and VPC are probably the most relevant topics (in my opinion). A recurrent topic in LA practice exam was SQS but there was hardly a couple of questions about it in the exam.
And yes, I have been working with AWS for almost four years now, although only with EC2 instances and S3 for storage. Taking the exam has helped me to discover a lot of new services!