Hi there, sorry I can only speak for RHCSA, but the principle is still the same.
Yes it is worth getting if this is your trade or career specialty. The course is 5 days with the last day used for the exam. The exam is packed full, so if you are relying on man pages, you will be likely to run out of time. Success is dependent entirely upon your previous experience with RHEL, and so I recommend downloading centos and practice performing all the types of activities they list on the website for the certifications until it is second nature.
I hold a current RHCE, but it will expire with the Redhat 7 release. When I did the RHCE exam I found it very easy and straight forward. I do work with RHEL every day, and the questions/answers are Redhat Specific, BUT if you have bad habits like me, and you are use to doing things your own way, you need to make sure you know the "Redhat way" of doing things.
As a sysadmin and/or security professional dealing with linux everyday, I still think that RHCE is one of the best certifications to complete as it demonstrates practical knowledge of the OS.
The Rapid track course is highly recommended if you want to "Redhatify" your current linux skills ;)
Thanks for the replies guys, I currently spent a good chunk of my time using CentOS at my work, so i'm familiar with the operating system and technologies, would just need to look at learning about the stuff we don't really use.