I have always made the standard buttercream with powdered sugar, butter, etc. This was a complete change for me when I tried it today. The taste is so mild, it's not very sweet at all, and really lets the cake and filling shine through. The perfect accompaniment to a fabulous cake recipe. Warning though! I made this in my stand-mixer and it was WAY WAY too much icing for it to hold. I had BC icing everywhere. If I were to ever make this again it would only be if I could use a commercially sized stand mixer or I would cut the recipe in half. After adding the sugar mixture I ended up scooping out half of the mix into an XL mixing bowl and then basically did two smaller batches and mixed them together at the end to ensure all ingredients were incorporated into the full mix. The icing was good but not sure it was worth all of the complexity, time, $, and mess it created.
I'm making this icing right now. So far it's looking beautiful and light. I am having the same problem as hrnewbie with it being way too much for my mixer. I also had to scoop out a large portion and am doing it in 2 separate batches. The time it's taking to mix both batches will be about an hour. My mixer is already really hot after 30 minutes. I do think this will be worth the time, money and mess though if it turns out well because people really just don't like fondant or the sweetness of most buttercream frosting. I will need to make them in 1/2 batches from now on though.
Ok, I have iced the cake. It is absolutely wonderful, light and smooth and light tasting. It does not appear to crust. It does leave a slight oily film in my mouth from the butter, but I think that's just normal for buttercream icing.