I would like to use it to produce fully static executables for simple utilities written in Common Lisp, but I haven’t successfully gotten it to work yet. Basically, in any case where a 50 MB SBCL binary would be overkill (eg performance is not critical and portability is the top concern).

I’ve also read elsewhere that ECL runs on OpenBSD, where other CLs have traditionally not been fully featured.

Edit: also seems like it could help with compiling to WebAssembly (again, when performance is not critical), although I think their work there is not complete yet.