I work with a lot of designers and copy editors other non-programmers who can't produce well-formed and valid structured text files by hand using the rudimentary tools they have available to them. TextMate and Coda and the like don't cut it, but designers don't know there's anything better. You can coerce JEdit to support some of this with enough plugins, but it's a usability disaster (overly complicated, no native OS integration, etc) and it's still missing a lot of Jetbrains functionality.
I would love to be able to point these people to Jetbrains, but all the project-based Jetbrains IDE's are way too complicated for non-programmer use.
Any chance of a Jetbrains standalone structured text editor for common formats like xml, json, html, css that doesn't have the project system or any hint of programming languages? All it needs is the standard Jetbrains schema-aware editing features, autocomplete, autovalidation, structure view, etc. It would just open files and edit them. No project setup, no webapp infrastructure choices, no server setup, no project structure viewer on the left, no knowledge of directory structures beyond resolving relative links.