I think the editor is there for inserting a littlebit of code here and there (the way designers probably use Hype).
Most developers already have a favourite editor.
I don't have a problem with using several tools for a project, in fact, that's part of my normal workflow. Editors, terminals, commandline tools, etc. - I've never been an IDE guy, and don't see the "need to stay within the app" at all.
Dedicated tools which are good at their specialty and work well together - what's not to like?
That being said - I won't mind if the editor in hype gets more features, it's just not very high on my personal (and therefore insignificant) priority list.