I also wanted to try the recipe as it was written, just to make sure I would be able to get it to turn out as expected, so I didn't want to add anything else. Also, I had read that MMF would take on the taste of the marshmallows, so thought that would be sufficient. I guess there's a reason I've never been a huge fan of marshmallows by themselves. 
I found it bit sweet and tasteless, so next time I think I will add some flavouring to the marshmallows by replacing some of the water with whatever I decide to use.
I'm really happy with the way it turned out, otherwise! I rolled out a bit just to play with it, and tossed it around like a raw pizza crust, and it was awesome! I usually use Satin Ice (buttercream flavour...yum), but have been experiencing a bit of elephant skin and tears, plus it's expensive, so gave this a go. I'm glad I did! I can't wait to actually use it on a cake! 