In the early days of linux I had trouble getting things to work with other distros. Slackware just works. I also learned more, because you are closer to the configuration files.
Yup, it's one of the simplest distro with a BSD spirit. I know that package dependency handling is considered to go against the simplicity of Slackware, but I think one of the main reasons why Slackware is lagging in popularity is because of the lack of a package manager that handles dependency resolution like Gentoo's emerge or Arch's pacman.