Users can defintely update their own details. If they have access to the back end they can select My Account from the menu and change all their details there. Most users however will not have access to the back end and so you will need to set up a front end My Profile atom for them to change their details. As long as they are signed in they can use this atom to change their details themselves and you save youself a lot of time. If you need any help with setting up atoms there are several help files on the subject at help.xpor.com