Given the fact that most people who will be programming/developing on the Imp are going to have to to be multilingual fluent and semi-sophisticated, i.e HTML + javascript + php +mySQL + JSON +AJAX, etc., whatever, not to mention some level of hardware interface experience, I would suggest that Electric Imp spending time on an “easy to use” IDE is not best use of resources. My experience to date is this will always be a “some assembly required” product. Cater to existing, professional tools and don’t worry about the newb. This is not Raspberry Pi or Arduino. Too many layers and interfaces are required to get a production app running.
I could live with a git interface like Amazon EC2 or even just an Eclipse library. Focus on the libraries and the hardware, don’t mess around with trying to re-invent the wheel. I’m an emacs guy from way back, even that with autotools would would for me!
Suggest you focus on the cloud interface with a clean API and debug hooks, and let folks build to existing IDE interfaces.
See:
http://nutty.sourceforge.net/
http://wiki.iv-multiplayer.com/wiki/index.php?title=Notepad%2B%2B
http://wiki.iv-multiplayer.com/wiki/index.php?title=Eclipse
YMMV,
Paul