The HP-Compaq merger did spend a lot of time and money evaluating the impact on customers before executing their post-merger IT integration plan. Between the announcement and close of their deal, they held focus groups and conducted surveys to assess what customers were worried about and how they hoped the combination would benefit them. Then, integration plans were designed to meet clients’ needs. And where changes had to be made that were not immediately in the best interest of customers, communications plans were executed to explain why these decisions were made.
HP-Compaq also used a M&A integration approach called “Adopt and Go” for making decisions regarding internal processes and IT systems. Rather than debating for months about whose processes were best, they simply agreed on one and went with it. As a result, they moved their merger forward quickly.
Speed is very important. Like employees, customers have "me issues" too. And, they have expectations regarding how soon their "me issues" should get resolved.
Studies done on customer satisfaction in mergers say that customers typically expect merging companies to have the majority of their "customer-facing issues" resolved within 100 days post-close. They will be pretty tolerant of mistakes, glitches, and bumps up to that period, but after about 100 days, they expect things to be running smoothly, if not perfectly.
Merging companies that take longer than 100 days to iron out their customer issues begin to experience dramatically rising customer defection rates. We sometimes refer to 100 days as the "customer tolerance point."
Now, of course, this doesn't mean that you can be sloppy, arrogant, or indifferent to customers during the first 100 days after close...