I've never had any porblems with jagged edges, but I don't use any of the methods here. I still use sprocket and when I make widgets I copy them from my mockup, place them in a psd file. And to make the alpha channel I duplicate the image and fill it with white. When I copy it, I have a action on F12 that index the colors and copy it for me, then I just paste it into sprocket. That simple.