The Arch Build System is utterly wonderful. All you do is define a PKGBUILD and it will handle downloading sources, compiling them, and creating a package. It's so simple that once you've done it a couple times it's basically fuck-all effort to create them for whatever you want.

So say I wanted to have dmenu on my systems with a custom colour scheme. I make the colour scheme changes as a patch and then create a package on the AUR like so: https://aur.archlinux.org/packages/dm/dmenu-dogs/PKGBUILD

Then all I need to do is run pacaur -y dmenu-dogs (pacaur is an AUR helper, which automates the process of downloading the PKGBUILD + any patches/local sources, running makepkg, and installing it) on my other boxes and it sorts everything out for me.

Pacman itself is also very lightweight and fast, and has a very simple and clearly separated API. Want to know what package owns a file? pacman -Qo /usr/lib/blah. Want to check a package has all it's files? pacman -Qk mypackage. Anything removing is -R, anything querying is -Q, anything installing (syncing) is -S.

The last thing I love about Arch is the wiki. It is fucking AMAZING. There are well explained and thought out posts detailing how to install and configure a vast, vast range of software. I even refer to it when I'm not using Arch.