While back Daniel Barlow explained why emacs is the best desktop environment he has used. I agree: emacs is the best desktop environment I’ve used, too. (Forth, Lisp Machine and Smalltalk users may be able to say different with reason, but few others.)
These days, a full blow Common Lisp is a relatively small application: Starting CLISP to evaluate an expression takes only 2.5 times as many system calls as it takes ls to list a single file.