I now use Swiss Meringue Buttercream on most of my cakes and cupcakes when customers request something other than ganache and fondant. It holds it's shape well and tastes amazing. Awesome. Fabulous. I can't stress how freaking fantastic this stuff tastes. It might seem like a fair bit of mucking around but it's not really and the end result is worth it. This blog post has the recipe I use all the time as well as the answers to any questions you might have - Swiss Meringue Buttercream Demystified
Here's a picture of a recent cake I made using it (sorry about the size, it's from my Facebook page and I don't know how to resize it):
If I want to make a crusting buttercream I do the following:
1 kg icing mixture
365g vegetable shortening (Frymasta, Copha or Solite)
1 tsp butter flavour
1 tsp vanilla essence
1/4 cup to 3/4 cup boiled water
Beat shortening until really light and fluffy, add 1/4 cup water and butter and vanilla flavours and beat again. (If your shortening is still hard or has little lumps, add the still hot boiled water and mix on very low until it starts to incorporate, then on high to fluff up. The hot water will help get rid of any lumps) With mixer on low, slowly stream in icing mixture (no need to sift if freshly opened packet) until combined. Then turn up mixer and beat until smooth. If the mix is looking dry and bogging down my mixer, I add more water until I get the consistency I want. The amount of water needed can vary greatly with temperature and humidity.
Here's a cake covered with this recipe, you can see it's not as glossy or smooth as the SMBC but it still tastes pretty good!
Neither are too sweet and I get rave reviews about both.