If you exclude the M&As involving large software companies, which seem to be the usual topic around here, then I could tell you that such processes - if compani

If you exclude the M&As involving large software companies, which seem to be the usual topic around here, then I could tell you that such processes - if companies are, for example, in segments such as manufacturing, finance, insurance, consumer products or media (that I know of), one of the most difficult parts consists/ed in systems (back end, front end, end users) convergence or absorption, with people aligned and committed to assist/support the efforts. In all scenarios, without exception, I was part of an M&A (and even divestitures, at time), on the IT side, the companies lost quite a few players (on the "acquired" side), due to frustration of not being able to create or produce as prior to such events, allegedly because of new IT environments. We tried everything - from spending days at the side of critical engineering or R&D or Sales & Marketing departments, to attempt to comprehend and create similarly supported new systems, to preserving parallel systems, for a while - and some people still didn't feel compelled to "change" how they were doing things. Unfortunately some of those were the ones in critical positions, which may have originated the ideas behind the desire for acquisition, and also able to choose alternatives, outside, i.e. changing jobs - as individuals - even if to then change IT systems in a new company, appeared as more acceptable than learning alongside the "acquiring" teams.