First, I wanted to say how much I like the measurement tool. So simple and powerful.
Some small wishes and thoughts:
(1) When double-clicking a glyph while in the measurement tool, it would be nice if this activated that glyph. Just like in the select tool.
(2) I would leave away the minus in the red difference figures. I do not think this information is relevant (also, it is obvious).
(3) To go one step further, for purely vertical or horizontal elements, the zero could be dropped, to un-clutter the interface even further. One could even make all the red figures absolute distance values instead of two-dimensional diff information, I personally would find that more useful.