a worse user interface, or ignores some other part of user experience
Many people say that most things that aren't emacs (or vim, depending on their religion...) have bad user interfaces, myself included. The keyboard-only way of working is very nice if you can get the hang of it. (Emacs is hard to begin with.)
That said, SLIME is basically the canonical Common Lisp editing environment and many the environment for other dialects emulate many of its features (e.g. Geiser for Racket), were you using one of those when you were using Emacs with a Lisp?
I used Emacs very shortly, only as a text editor. The learning curve is horrible -- my impression is that you need to memorize dozens of new keyboard shortcuts (and unlearn dozens of keyboard shortcuts more or less consistently accepted by many other applications, also clicking right mouse button for a context menu). There seem to be some interesting features, but again only for those who memorize the keyboard shortcuts. And the whole design seems like a character terminal emulator.
So the problem is that it looks interesting, but one has to pay a huge pric...
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