Hi, I've just discovered IEP : great product, you are on the right way !
I use SciTE (Scintilla based too) as main editor, for 10years, on Linux/windows. Just because, it's cross compatible, power configuration, and pretty fast !
Sometimes, I try to change ... Sublime, Atom, etc ... but can't ;-(
IEP is on the right way. It seems perfect for python power users.
I really love : the interaction side (cellule, selection, main script), the workspace browser, the file browser, the shells, the completion, the hackable side of iep, the tools concept, ability to edit/run a script without saving it, sandboxed process
But for me:
It miss some shorcuts : duplicate line, toggle comment (I'm looking for patching that ...)
It miss syntax colorations for other kind of files (html, css, js, xml, json ...) : Scintilla is really perfect for coloring theses ;-).
it should stay as light as possible, and avoid to be a bloatware one day (tools and/or extensions is a good base to add others no common features)
it should be easy to export configurations (shortcuts, prefs, colors ...)
BTW I will use it as a second editor, for explorations, prototyping, interacting ...