Recs.
Updated
Arch Linux keeps things simple - it's lightweight, without the cruft of most other distributions, and completely flexible. These traits make it a popular distribution with many more experienced Linux users.
SpecsUpdate
Pros
Pro Simple by design
Arch Linux is actually incredibly simple. It's really just a partition scheme, package manager, Linux kernel, file system, systemd and the bare minimum of utilities needed to easily set up your hardware.
This makes it super simple to build your desired system using binary packages because there no bloat getting in your way when installing or configuring packages.
Pro Fast and simple package management
Pacman has performance advantages over apt-get and yum in both database operations (thanks to being written for speed) and download times (by virtue of using better mirrors than other distributions tend to select by default). There are also fewer default repositories to download from, and all package management is combined into one tool instead of being split into dpkg, apt-get, and apt-cache like on Debian distros.
Pro Excellent documentation
Arch's goal of simplicity means there's usually one preferred way to get things done - through organized and well documented configuration files. This focus, combined with the community's recognition that configuration files can be intimidating, has resulted in excellent documentation that's accessible to newcomers, and very instructive about how Linux actually works. The documentation is often so thorough that, when searching for solutions to problems while using other distributions, such as with video card drivers, oftentimes you'll find the most effective solution in the Arch Linux wiki or on the forums.
Cons
Con Too many package upgrades that require manual intervention
Every year or so there is a update to ArchLinux that will break your system unless you first read the front page of archlinux.org. This happened with SystemD and with a few other updates that require you to do prior steps befor pacman -Syu.
Con Documentation only makes sense if you know how to adjust it
While the documentation is a very valuable reference for experts, the recipes often don't actually work on your own computer. Some articles are outdated, incomplete, contradictory or duplicated. Only if you are expert enough to know which steps to skip, to adjust or which other documentation parts to plug in, you can make it work.