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.
Pro Helpful for understanding how Linux is installed
Arch does not come with an automatic installation process. The user is expected to walk through the installation steps published on the Arch wiki. This is very useful if, later, something happens to the installation as the user will be more familiar with the foundational steps required to get a full blown Arch installation working.
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.
Pro Excellent package management with the AUR
The AUR is a repository with a very extensive catalogue of build/install scripts that are contributed by users. While these scripts are inherently less secure than conventional packages maintained by a distro's authors, it's still way easier to verify the security of install scripts than it would be to write them yourself. It's very usefull.
Pro Helpful community
If searching through the wiki or the forums for any problems turns nothing, any question on the official forums, Arch subreddit or the IRC channel will be answered within minutes. There will probably be no hand-holding however, Arch users prefer to point anyone to a resource that may help them instead of trying to outright solve their problem in a forum thread. This is quite helpful for people who want to really learn how their system works but also for other people who may stumble in that thread considering how most problems don’t have a universal solution.
Pro As slim or copious as you want it
Arch keeps its core repositories slim and free of unnecessary dependencies. At first installation only a bare system is set up. You can easily get the other applications through the package manager. The repositories are nearly as full as those of Ubuntu, while they are often more up to date. That way you don't have to waste time with software you don't need or want.
Con Not for the faint of heart
Arch only holds your hand a little bit of the way. While documentation is great, you are expected to know what you're doing. The result is that when you find the solution for a problem on a forum or elsewhere, the response may be completely over your head. If you're not well-versed in Linux, what would be a minor issue on another distribution can become a drawn-out research project on Arch, as you learn all the inner workings of the operating system, until you understand it well enough to solve your problems yourself.
Con Rolling release requires bandwidth
Arch uses a rolling release model for updates. Unlike, for example Ubuntu where a new version is released every six months, packages are updated when they are ready. The advantage is a very up to date system and that the work of upgrading can be spread over a longer span of time to a point where it is hardly noticeably effort. However it can be difficult for people without a high bandwidth connection, or with limits on how many GB can be downloaded imposed by their internet service providers. A GB a month of downloads is quite possible.
This can be somewhat offset by Arch being lightweight, besides the relatively small core, the user selects what is installed (and has to be updated).
Con Fragile packages
Updating an Arch system is always a gamble. The problem could be as simple as a package having a bug causing a program to crash on start or it may be something bigger like the WiFi or Bluetooth no longer working. There is also the slight chance the system may not even boot at all after a large update.
If the user does not plan to read the forums weekly/daily or update fairly often, things can go wrong very fast.
Con Occasional upstream package bugs
Most package maintainers look for issues that the packages might have ispecifically for arch. Which means if a package has a bug that applies to all linux distros regardless of the flavor, the maintainer may not be able to: A) catch it before pushing a update or B) have to wait for the packages developers to fix it.
This is a minor issue because most issues are often patched before the end of the day if many users rely on it, or if its a less used package there will be specific troubleshooting instructions on the arch site.
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.
Con Not so great overall
Apart from the ArchBuildSystem/AUR, which brings you very quickly newer package versions, there is not really much where Arch Linux shines.
- You get better package managers with other systems.
- The most Linux distributions are far more stable than Arch.
- You learn more about Linux by using LFS or a source based distribution.
- You can customize the system much more in LFS or Gentoo.
Con Multiple Aur helpers
Arch has strict reasoning behind what goes into the official repositories accessible by pacman. As a result, many other projects end up in the Arch User Repository (AUR). Effectively using Arch, and getting easy access to all of the available software, means either manually downloading and installing from the AUR, or installing an AUR helper - these work along side the main package manager (Pacman), but are a bit less standardized or heavily supported.