A couple of weeks ago I had the need to logon to my Project Server instance through the project client as another user. Usually I would check the ‘Enter User Credentials’ option on the login screen and enter the credentials to login with. However, in the Project 2010 client the ‘Enter User Credentials’ check box is missing. After a quick poke around the forums and reading a footnote on this article, it seems it still is possible to logon as someone else, but it’s a little less obvious.