Traca, actually I've had great success with buttercreams, it's the weather
that messes with it...that and my own lack of sense.
Like you, I tend to read, read, read before leaping into a new method. In this case, I screwed my own positive results because I tasted the finished lemon buttercream and it was so wonderfully "lemon curd-ish" that I thought (always a BAD thing) I could add a few jars of my own home-made lemon curd.
In other words, I changed the stability of the buttercream myself.
And while the icing was perfect when ice-cold, once it hit heat on the drive to the event, then sat for 1.5 hours near a door that the volunteers kept opening, it softened too much.
Luckily I was able to serve it before it all slide down....unlike the 6" topper that I brought home with its delicious lemony icing puddling around the cardboard base.