I do use it, as it’s the default kernel of the GNU Guix distro which I use daily.
The main drawbacks is that it forces you to choose your hardware wisely, using e.g. h-node.org to be sure it’s compatible. Otherwise, this is quite exactly the same kernel, just really free as in freedom.
It never proposed GNU Guix to me. Quite unfortunate, that’s my daily driver and I love it.