I'll let you know how hard it was when I get my score back 😉
I imagine it would be pretty easy if you were taking it at the tail end of an emergency medicine rotation, but as a psych intern, I had to study for it. (Unfortunately, I was sick and vomiting for half of my scheduled study time, so I didn't get to study as much as I'd have liked to.) I do think it's probably best to take it during intern year before you're too far removed from the rest of medicine. I took it after my EM rotation, and that was good practical prep.
Still, I found the test highly annoying. Many of the questions ended in "what is the immediate next best step in the management of this patient?" then had a list of things that in reality, you'd write on the order sheet all at the same time and they'd get done in whatever order the nurses got to it. So the question was basically "read our mind." 😡 Oh and yeah, the xray images were absolutely horrible, no matter I did to the monitor. 😡 😡 And I only stayed to do the optional survey at the end so I could vent about the images, and then there was no free text space to do it. 😡 😡 😡
Anyway, the best thing is to do lots and lots of questions from usmleword.com in tutor mode (gives you the answer and explanation after you do each question) so you can learn what they're looking for. Wish I had had time to do more of them. And of course do the CCS questions on the CD to familiarize yourself with the format. The other thing that helped was this little Blueprints book about the CCS exam. Explained the confusing format and outlined a simple strategy to do them, and you can easily read it one evening. Still I got flustered and f'ed up my first one. Sigh.