The latest version of Blue can be downloaded here:
http://www.robertknight.me.uk/files/darkbasic/blueide_rc4.exe
In my view the main advantages of Blue over the default editor, is the saving system. In addition to saving everything on save, it creates a backup each time you compile. If you want to "save" that particular version of the source in case you make experimental changes, just go into your project folder and rename the backup folder to "Backup <date>" for example.
The features I use the most are Goto Definition & Search For References which allow you to easily navigate around the source. Code Snippets are very handy too.
Oddly some of the minor differences really impact the usability. For example Blue has an "Open Project Folder" link which opens the current project's folder in Explorer. The function list in the original editor is displayed in the order the functions occur in the source code, Blue displays them in alphabetical order. The default IDE lacks a "Run Only" option. The original editor uses seperate windows for different source files, Blue uses tabs.
Anyhoo, I'm obviously biased, so ignore me. Twilight has quite a few of these features as well.
BlueGUI:Windows UI Plugin - All the power of the windows interface in your DBPro games.