Linux Kernel Configuration Code Maturity Level Options

If you select this option, it will enable the inclusion of incomplete or experimental device drivers or protocols. Otherwise these will not show up in the configuration menu.

In my own personal experience, if you are using something other than a very mainstream Intel box, there is probably something that you might need which still hasn't been declared stable and thus you will need this option.

Another note; stable seems to be in the eye of the beholder and there are device drivers that have been declared stable for years which are not, and there are device drivers which are still labeled experimental but which actually work quite well.