After many years of love for beautiful interfaces ("oh, look, how beautiful and shiny (i.e.) `PCalc` is"), I realize that what matters to me is my data and a versatile interface that allows me interact with my data. Emacs + Lisp are this minimalist, yet extremely versatile and powerful interface to get almost everything done in working with a computer: Write text of any kind (from code to novels), manage projects and keep a personal wiki with org-mode, create overviews with (ascii)tables, write documentation, automate all kinds of workflows using Emacs Lisp.
In a sense the ZEN or essence of interfaces.