The above command for Guix before the changes (commit e19a539):

--8<---------------cut here---------------start------------->8---
[...]
Loading /gnu/store/lj09yx56hgsq9l4ajk5wlxsk4vbrympk-profile/share/emacs/site-lisp/undercover-autoloads.el (source)...
Loading /gnu/store/lj09yx56hgsq9l4ajk5wlxsk4vbrympk-profile/share/emacs/site-lisp/with-editor-autoloads.el (source)...
Loading /gnu/store/lj09yx56hgsq9l4ajk5wlxsk4vbrympk-profile/share/emacs/site-lisp/ws-butler-autoloads.el (source)...
Loading /gnu/store/lj09yx56hgsq9l4ajk5wlxsk4vbrympk-profile/share/emacs/site-lisp/yasnippet-autoloads.el (source)...
(9.971024566 159 2.763721703999999)
--8<---------------cut here---------------end--------------->8---

After the changes:

--8<---------------cut here---------------start------------->8---
Loading /gnu/store/fwji52vg31xmdkc2z5cbjrfza7fxndr5-profile/share/emacs/site-lisp/undercover-autoloads...
Loading /gnu/store/fwji52vg31xmdkc2z5cbjrfza7fxndr5-profile/share/emacs/site-lisp/with-editor-autoloads...
Loading /gnu/store/fwji52vg31xmdkc2z5cbjrfza7fxndr5-profile/share/emacs/site-lisp/ws-butler-autoloads...
Loading /gnu/store/fwji52vg31xmdkc2z5cbjrfza7fxndr5-profile/share/emacs/site-lisp/yasnippet-autoloads...
(7.435941036 143 2.406266451999999)
--8<---------------cut here---------------end--------------->8---

I think it's neat that all of our Elisp is byte compiled; it's something
that can be done without fear on Guix, given that when the Emacs package itself
changes, all the Emacs packages are rebuilt.  It could also find issues we'd not
know existed otherwise, as I found out for the emacs-cl-generic package.