cl-simd is actually intended to be a contrib for sbcl,

Maybe I am wrong, but I would prefer a single macro which gives you the ability to inject the machine instructions into the code stream. I feel that this is a bad style, to mix CL with assembler, but it could give the ultimate code optimization possibilities for the people who know what they are doing and why do they need it. This is especially true for SIMD.

P.S. Btw, is there some kind of official (or nearly so) mirror
of the new sbcl repository on github? It would be a convenient
way to save some space via the fork feature of that site.
I forked Anton's repository, it is mostly up to date with the upstream + builds natively on Win64: https://github.com/akovalenko/sbcl-win32-threads