CPO is a good program, but its not a substitute for getting the car inspected by an experienced BMW mechanic before you buy it. In reality the value in the CPO program is more in the warranty than the "multi point" inspection. No matter what BMW says, how much attention CPO cars get in the fixing/reconditioning phase of the "certification" process is highly variable depending on the dealer. Some dealer care and only buy good cars and fix them up to be like new, some don't care and will try to pass marginal cars off as CPO if they can.
I got a CPO a few years ago and although it has been a good car, it had lots of little issues that the previous lease holder just didn't bother taking care of and weren't paid much attention during the CPO process. Because I had the warranty, the dealer ended up fixing them with no charge to me, but it was a pain to take the car in multiple times right after I got it.