Now, I dislike Maya, I use 3ds max. But I noticed that maya had a nifty feature that would allow me to transform the gizmo along an edge. See image below for explanation:

The white arrow shows the direction I want to pull the edge, in the first image you can see that I would have to adjust X and Y to move it, but that means I would have to eyeball it to keep it even.
I rotated the objects pivot in the second image, but as you can see this is hard to get really accurate, id prefer a simpler way.
Thanks!
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http://www.funkybunnies3d.com/tools.php
Does exactly that! It's gold, I use it daily...