If you've ever worked for a company that's acquired one or more companies or has been acquired by another firm, you've probably been witness to some deals that have generated a decent amount of value and others that didn't work out so well.

Now, McKinsey & Company has released the results of a study where they examined patterns of deal sizes and the frequency of deals among the world's top 1,000 companies by market capitalization as measured by excess total returns to shareholders. According to the authors of the study, "it seems not to matter much whether companies completed one large deal, many small deals, or few deals." From a value-creation perspective, the size and number of deals matter less than the discipline that's applied to them, including how they're priced, integrated, and managed.

While the results of the study seem logical, they also offer constructive lessons to CIOs and other CXOs regarding the importance of applying stringent due diligence to deals, including closely examining the cultural fit between organizations as well as the importance of properly integrating the IT architectures of the respective organizations.

According to a separate study conducted by A.T. Kearney, 58 percent of mergers have failed to deliver "substantial" returns to shareholders. With millions of dollars of potential IT cost savings and efficiencies on the line, it's easy to see how the operational side of the M&A process often under-delivers when systems integration and consolidation isn't carried out to fruition and unretired systems continue to function in perpetuity.

Of course, IT and other types of operational integration efforts are only one dimension in the M&A benefit equation. While there are plenty of opportunities to remove redundant systems costs and other types of IT overhead during the post-merger IT integration phase, there are also opportunities to identify systems and processes that can be adopted by either the acquiree or the acquirer in a deal which either benefit the combined company or can lead to efficiency improvements for the acquired company if it's to continue operating as a semi-autonomous entity.

What have your experiences been? What aspects of mergers and acquisitions that you've been involved with have led to solid performance outcomes or failed to materialize?