Yes, it is relevant. For example, Guile powers an entire GNU/Linux distribution[0] where Guile is used for the init system, initial ram disk, and package manager.
It's quite usable, but like anything could be better. I run GuixSD as my daily driver OS on a laptop and desktop and it's very comfortable for my needs. OS upgrades can be easily rolled back in case I screw something up so I feel more confident to experiment with my system.
[0] https://www.gnu.org/software/guix/