Data management friendly i.e. event trigger when 'X' icon is click, window can be always on top until event append, access to window properties like oWindow.save, oWindow.content, etc.
Allows the ability to reproduce a fat client graphic user-interface (GUI) on a thin client. Security per user/group easy to implement. Ideal for Business Intranet Site. You are not required to open other browser tab or suffer the loss of current user credentials and session. This end result is a real MDI. This is what corporate business on the intranet has been missing for a long time.