There are some clever solutions to this problem out
there but they are either unsupported or they require some client side hoops and hurdles. Alt Login works in a different way. It basically provides the simplest of UI extensions in a single Elements XML file and packages it as a standard SharePoint farm or sandboxed solution. Because Alt Login follows a standard solution pattern it is fully supported.
When the Feature is activated just select the 'Sign in as a Different User' item from the personal actions menu to switch user identities. That's it, told you it was simple!