Not sure what you mean by "live editing of inline data structures" here (care to give an example?), but the interactive debugger in Emacs/SLIME can do quite a lot of nice things, including modifying arbitrary data on the fly, live.
For instance, if I have a hashtable returned from a function I called in REPL, I can inspect it and modify its values and properties. Also, within the REPL itself, text is "smart" and copy-paste tracks references, so I can paste the "unreadable objects" (i.e. #<Foo 0xCAFECAFE>) directly into REPL calls and have it work, because SLIME will track the reference linked to a particular piece of text output.
The presentation based REPL in Emacs + SLIME was inspired by the Symbolics Lisp Machine presentation feature.
But I can assure you, there is a difference of a REPL feature in an editor and a GUI using it system wide, as on the Lisp Machine. Both in depth of the features, integration and the feel of the user interface.
Check out this video (which I made some time ago), which shows the presentation UI from an application perspective (here a document authoring system) and as a bonus, the application integrates Zmacs (the Emacs of the Lisp Machine)...
Think of the Documentation Examiner a version of Emacs Info. Think of Concordia as a version of an Emacs buffer editing documentation records. The listener a version of the Slime listener. You can also a short glimpse of the graphics editor, IIRC.
Dr Racket's REPL is probably closer to the experience.
Also very few IDEs enjoy the same edit-continue experience, maybe commercial Common Lisp environments.