When I normally edit my code (such as php or javascript), I use an editor that uses syntax highlighting. It is nearly impossible to get the code correct if you try to edit it in the SS code object. The main reason is that the formatting is difficult to read because it usually gets wrapped in "awkward" ways. The other issue is that there is not syntax highlighting.
I don't expect SS to be all "fancy-like" and start highlighting syntax, but I would like to see an option to use an external editor for editing code objects.
The way I envision this is that there would be a SS configuration option to point to the executable of your editor. When you edit a code object, it launches the code in the selected editor. Not sure of the logistics of how to save the code from the external editor back into the SS code object, but that is where the SS development dream-team does some creative thinking.
This feature addition would make it easier to edit/maintain code objects that contain a lot of scripting. Because of the current editing hassle, I never add much code into the SS code objects. Most of my code objects are "server side includes" which point to an external file containing my code (which I edit in an editor).
The Code Editor does have a File->Open menu command, so you can still edit your code in a syntax-highlighting editor, save it, then import it into SS. This method also gives you a back-up in case your project gets corrupted, or allows you to use the <script src="...> method to include an external file.