Sugarshack's recipe is just an all-shortening one, if I rmember correctly. I have my own opinion about no butter in icing, but that aside, i've seen that kind of icing slide right off a cake in the Virginia heat. So it depends on where you are and the actual weather.
I used that recipe on all my cakes for several years now without any problems. I live in NE Ohio which will reach into the 90's June-August regularly. Last summer I deliveryed an all buttercream cake to an outdoor venue in over 90 degree heat without any problems. The photographer sent me a couple pictures of the cake she took during the reception (a couple hours after delivery) and the cake still looked great. I can understand you have an opinion about "buttercream" with any butter but if the recipe works for the envirornment it is used in and tastes great - I have no problem using it. My brides love it and I never worry about melting.