Since its first beta release in April of 1993, the Slackware Linux Project has aimed at producing the most "UNIX-like" Linux distribution out there. Slackware complies with the published Linux standards, such as the Linux File System Standard. We have always considered simplicity and stability paramount, and as a result Slackware has become one of the most popular, stable, and friendly distributions available.
Ranked in these QuestionsQuestion Ranking
Uses stable, plain-vanilla packages from upstream.
Pro Ideal to learn more of Linux
Follows the original Linux roots. It still sees Linux as a free clone of UNIX so the distribution tries to be UNIX-like.
Pro Strong adherence to UNIX Principals
Pro Package management
Uses standard tar archives with shell scripting as packages.
Pro Oldest surviving Linux distro
Besides Debian (which was first released in August 1993), it is the oldest still maintained Linux Distribution and was first released in July 1993.
Pro One more distro which is init based
Some users don't like to install systemd based distros because they increase booting and processing speed.
Pro No systemd
Con Not user-friendly
It is made to be KISS (keep it simple, stupid), so you have to do everything by hand.
Con Large size live ISO
One needs to vain 3GB+ data for downloading one slackware ISO.
Con Niche/small community
Slackware is its own niche and has a small community.
Con Very slow release cycle
Hasn't updated in 3+ years.
Con Narrow repos
Doesn't offer the same amount of options as other distros do.
Con Dependency issues
When it comes to dependencies, Slackware shows more issues than many other distros.