The "shallow mental model" most likely refers to fewer initialization files and locations. When starting out, most everything you need is in /etc/rc.conf . Also, Arch and its package manager don't use /usr/local/, instead simply using /usr.

"It really does take time" most likely refers to the fact that you are responsible for building up the OS yourself. So unlike in an OS like Ubuntu, where you do not have to know what a window manager is, or what an xorg xserver and client means, you'll have to learn it all along the way.

Fortunately the wiki makes figuring everything out managable, and I found it an enjoyable to spend a couple days with different software[1] and a programmable tiling window manager[2]. The end result is a fast-booting custom tailored system.

[1] https://wiki.archlinux.org/index.php/Lightweight_Application... [2] http://awesome.naquadah.org/