I'd say it would already be great if they could bring newcomers to Clojure: people who are rebutted because of Emacs.

As to me I'd need, at least: ace-jump-mode, paredit, the powerful macro system and the ability to create my own rules for highlighting / overlaying text as easily as from Emacs.

Short of that I'll keep using Emacs. Now what I think: it's probably easier to add LT's "instarepl" to Emacs than to add one million lines of elisp code to LT so...

I fully expect someone to hack a "Clojure instarepl" Emacs mode one of these days.