It's well known that most mergers & acquisitions fail to deliver the expected outcomes for a whole range of reasons such as incompatible cultures, unrealistic synergy expectations etc.

However, this article from Grant Thornton US is interesting as it suggests that even companies who do M&A on a regular basis seem to go through the process as if it's their first time, inventing the integration wheel rather than leveraging previous experience and sticking to an integration playbook...