'EQUILATERAL-ness' of Triangles

This applet is an exploration of the 'EQUILATERAL-ness' of triangles. If you drag the vertices of the triangle, some measures of properties of the triangle are shown in the table on the left. Can you construct a measure of 'EQUILATERAL-ness' based on these measures? What other measures can you think of? When would those measures be better? What other questions could/would you ask your students based on this applet?