I used Gentoo around 2004/2005 and I keep very positive memories, I learnt a lot. Very attractive dist for developers because being source based, you can quickly test a patch in a system component (like eg. Wayland, Mutter, GDM) by just telling Portage (the package manager) to pick your patch and re-installing the package (re-emerging in Gentoo parlance). I even was able to contribute a patch for upstream Firefox that way (because compiling Firefox yourself from source is so much difficult).

I also built my own kernel as Gentoo favors that. I remember tailoring the kernel to my hardware (picking only the kernel modules needed to my peripherals), my resulting kernel was about 2 MB in size, while the corresponding kernels at that time for Ubuntu or Fedora were around 20 MB (because they need to blindly include all peripherals which any user may have) that meant 18 MB less memory in RAM permanently (good for embedded and systems with constrained memory).

After some years I end up switching to Fedora because I could not spend so much free time just maintaining my Gentoo distro (it's fun and you have so much control over your distro, but at the expense of more time spent on that).