I do like the Admin "Log In As" feature but there is a big downfall to using this - it counts the Admin as the "User" logging in. My leadership likes to look at the users & Last Log in Dates, but I can no longer provide this report since it is not accurate.
ex: Admin John Doe, uses the Log in As to check something on Jane Smith's account. Jane Smith last logged in on 6/1/2015. The Admin logged in on 12/31/2016 (using Log In As). If I produced a Last Log In report, it will show that Jane Smith logged in on 12/31/16, when she actually logged in on 6/1/2015.