ET's Info-Stew

"The Threshold Alpha command converts semi-transparent areas of the active layer into completely transparent or completely opaque areas, based on a threshold you set, between 0 and 255." That's what the GIMP documentation. Whoopee! So what?

I pulled this trick from the Comic Book Script-Fu: take some object on a transparent background (text is good), apply a 5-pixel gaussian blur. Then do a threshold alpha of 0. You'll get a sort of bubbly text:

Compare that with taking text, growing the selection, and filling:

Look around the x and you see that the bubbly text has more rounded corners. Not a huge difference, but if it's the effect you're going for, then hey. The Comic Book script-fu uses this method for the outline of texturized text.