Following on from T40416, I had a look through blender-addons-contrib, and found some opportunities for similar and other simplifications. I have grouped my changes into 3 separate patches.
Remove unnecessary imports:
Use Vector.length rather than calculating sqrt of vector dotted with itself: (oops, duplicate upload )
Replace various uses of math.sqrt with more concise math.hypot:
Some of these addons seem buggy. I trust I have not introduced any new bugs, at any rate. :)