I took this today and passed. I think the test could have been a bit better, some of the questions were kind of dumb imo. You
do have to be familiar with the inner workings of Nova/Swift/Neutron/Cinder/Glance/Horizon etc, so I wouldn't exactly call it easy. It's not really 'hard' though, you pretty much either know the questions or you don't.
Studying just involved messing around with Devstack for a bit, I also set up OpenStack from scratch. Thats a good way to familiarize yourself with all the parts. You can do it in a single VirtualBox VM.
DevStack - Deploying OpenStack for Developers
Heres what the cert looks like: