Ranked in these QuestionsQuestion Ranking
Pro Persistent changes
Changes you make in the configuration persist if you run from USB.
Standard tar archives plus some simple shell scripting produces modules that you can load dynamically into the OS for added apps and functionality.
Pro Modern desktop
Pro Small footprint
About 200mb, but with a full KDE4 environment and loads of useful apps.
Con Works slowly on old computers
Con Infrequent releases
Since Slax is maintained by only one person, releases are not that frequent. So it may take a while to get bug fixes or new features once you start using it.