1 Why I Use Gentoo
I use Gentoo Linux as my primary operating system. Gentoo Linux is a source based GNU/Linux distribution, which means that you must compile the source code for your specific architecture. Gentoo has long installation and upgrade times; but, despite that, there are a number of reasons why you might want to use Gentoo.
1.1 Version Slots
Gentoo has a slotting system, making it easy to switch between package versions, such as between PHP 5 and 7.
1.2 Package Manager
Gentoo's package manager, Portage, plus a number of accompanying tools, such
layman, make it easy to manage packages,
search for them, and add third party repositories.
1.3 Rolling Release Done Properly
I also occasionally use Arch Linux, which also uses a rolling release model, but it is a binary distribution. When installing a program in Arch, you are forced to first upgrade because the package version that is compatible with your setup no longer exists. In fixed release GNU/Linux distributions, forced upgrades may still be required, for the same reason. In Gentoo, the source code is pulled from upstream; so, as long as the source exists, you can install your desired program.
1.4 Choice and Optimization
Gentoo typically gives you choices about which major versions of a package
that you want installed. There are sometimes incompatibilities that occur
between packages, but if you really need a specific version of some code to
run a particular program, you might be better off creating a Docker
container. Gentoo also allows you to control the compiler flags and configure
options used when building a program. Gentoo is great for low power devices,
so long as you can cross-compile it. I ran Gentoo on an EeePC 1000HE for a
number of years and would upgrade by imaging the hard drive and upgrading the
image on my desktop in a
linux32, loop device,
Initially when I got the computer, I installed EeeBuntu, but the Unity
interface was slow and cumbersome. Installing Gentoo, which admittedly took
a few days, ran much faster. Upgrade times can often be sped up by farming
out the compilation; although, some programs will fail to compile when
Gentoo gives you a choice between OpenRC and the more popular Systemd for system initialization. I prefer most aspects of OpenRC over Systemd. Systemd's integrated logging is convenient, but its conveniences stop there. OpenRC does not do logging. You have a choice of which logging system to use. OpenRC's user interface is strait foreword and not overly verbose. I have not used both, extensively enough, to really form a good opinion as to which is better; but as a user, my preference is OpenRC.
1.6 Other User Testimonials
If you want another user's experience, Randal Schwartz and Aaron Newcomb, in their FLOSS Weekly show, conducted an interview with Jeff Horelick about Gentoo.