I've never used Sweetex (honestly, I've never even heard of it).  The reason my icing has become somewhat popular is because the zero-trans-fat works with it.  I never even noticed when crisco went to zero-trans.  Many folks have offered suggestions on air holes and grittiness (neither of which any of my customers or cake recipients have ever mentioned ..... not saying it is not there, just saying no one has ever mentioned it).  Some have found using warm milk helps.  I turn on the mixer and let it run (when I had the shop open, I'd turn on the mixer, then go to a store next to me or I'd go outside for a smoke break (when I smoked).  Since I stored the icing in a sealed container on the counter, I also found that after the icing "settles", it is smoother.  Just run a big spoon thru it a couple of times and you're ready to go.

To the other post, yes, I use it as a filling for my cakes.  I never had multiple icing recipes.  One icing fits all!!  Only time I made a diff icing recipe was when I was making chocolate icing.,