Impersonate a user

An Administrative user at a client has asked if there is a way for him to "impersonate" a user without having to log in as that user.    This way he could test the user menu and security settings without being logged in as that person.

Is there a way to do this?   

Are there Operating System tools that might allow him to do this? 

Actually, i think i found a way.    Open another browser window and log in incognito.    Are there issues with this?  I understand you have to log off for some changes to take effect.  

Can i propose my own answer as an answer Smirk.