I am studying for it right now. I looked up the stats and it seems to be a little easier than the CPA judging from the pass rates. The CPA pass rates look to average around 47 or 48%. The CMA pass rates look to average around 53 or 54%.
If you consider that 46 or 47% of people, who are probably degreed accountants with work experience in the field fail the CMA, it can't be easy. I'm doing a Gleim's prep and some of the questions are tricky.