It should be noted that a CMMI maturity level designation is not a certification. It may help to have some CMMI appraisal team experience to understand it (I do), but the designation is the result of an organization's self-assessment based on an appraisal model (SCAMPI) developed by SEI/CMMI Institute. When a company claims a certain maturity level, CMMI Institute does not say "we certify this organization (or organizational unit) is CMMI maturity level n." CMMI Institute says "based on our review of the result forwarded by the organization, a result approved by a certified CMMI lead appraiser, we conclude the organization appears to have correctly followed the SCAMPI method and met the standards the organization's appraisal team agrees they did."
An organizational unit is not CMMI-certified by an external certifying authority, it is appraised based on work of a mostly-internal appraisal team (usual exception is the appraisal team leader, a certified individual not employed by the appraised organization in my experience). I don't blame anyone for being confused on the "certification" label... I see it all the time. The title of the
My concern with CMMI is not the procedures and practices themselves, I think they are brilliant if implemented and the organization is resourced to handle it while not tripping up development teams. My concern is in self-assessment, that an inherent conflict of interest exists for the members of an appraisal team employed by the company they are appraising. A company that spends a lot of money preparing for and conducting a valid appraisal it expects a positive result for. But an accredited lead appraiser (again, not an employee of the appraised company in my experience) is not going to keep that distinction for long if they pass through insufficient/bogus appraisals, and that is supposed to be the check on self-assessment risks.
So it isn't the same as PMI, which gives a four hour exam to produce a quantitative, evidenced pass-fail score for a project manager and puts their stamp on a certification that the candidate knows the material with required proficiency and has met other work experience requirements. It is more nuanced and really comes down to how much you trust a given self-assessment.