This is actually pretty easy to do if the geometry of the object is allowing for it. The key is to use a higher Transparency Edge setting than you do a transparency setting (for example, trans of 1, edge of 3). Adding a bit of displacement can also really up the effect as well.

thou and I, my friend, can, in the most flunkey world, make, each of us, one non-flunkey, one hero, if we like: that will be two heroes to begin with. (Carlyle)