I've seen many IDEs over the past 20 years or so. The only one I have ever found compelling is XWindows running on unix. The text editor choices are great (most IDEs have a preferred editor the project people wrote themselves), the pasting of code between windows eases refactoring in completely intuitive ways, switching any piece of the development suite affects almost nothing else and needs no configuration (how hard does the IDE make switching from cvs to svn then to svk), complete stability, libraries of books on how to use the IDE, great scripting languages (perl comes to mind), incredible tools (grep, find, locate). I could go on.
Phil