"In simple words, Firefox Minefield is a playing field for
developers to continuously, often daily, update with the new things
they are working with; which makes minefield nightly builds often
unstable.
"From a user’s point of view this is a great way to try
out new options/features without having to wait few months for the
next release. When Mozilla introduced major enhancements to its
tracemonkey javascript engine last year, it was available on
minefield nightlies, months before stable Firefox release."
