What seems to be the most difficult is assessing potential cultural clashes. While firms like Vista Equity Partners require all employees to take a competency test, this seems to be done after the acquisition is completed. Along these same lines, I can imagine that you could only interview the most senior leaders (small sample size) to gauge the cultural fit of an acquisition.
Are there steps one can take to get a feel for say 70% of the organization prior to an acquisition?
