I shall be attempting my first ever cream cheese icing tomorrow, very exciting! So Ive been reading this thread thoroughly.
When it was first posted I followed the instruction to beat my IMBC on the slowest setting once the butter had been added. The recipe (Warren Browns) said to expect 4-5 cups. I got SIX! Was delighted

I was also glad to hear that you feel adding flavour reduces the butter taste. I am not a butter fan, and Warrens recipe tastes buttery to me. I would like to experiment with ratios as Linda talked about, but at this stage think Id better learn to walk before I run.
A couple of questions:
FromScratch: You do not refrigerage your SMBC. Ever? What if you are making it a few days in advance, do you still leave it out? If so, how long do you leave it out for before youd throw it away?
You also stated you have used your cream cheese icing on cuppies that have been out for 12 hours. How is this OK with the cream cheese content? I recently bought a delicious cupcake from a shop, and was told it was cream cheese icing. They do not keep them refrigerated, and said I could keep them out for three days. I asked how that was possible with the cream cheese content, and they said it was because the sugar acted as a preservative, kinda like jam. Everything else Ive read says cream cheese MUST be refrigerated, until I re-read your thread today. So my question is, if that is true, is there a magic ratio of sugar to cream cheese which makes it safe? And once the cream cheese is added into the IMBC, how long is it safe for? (I dont know if her 3 day rule was due to the icing, or the cuppie going stale).
As a point of interest in regards to the colour of butter, our cows here in New Zealand are grass fed, and our butter is VERY yellow compared to American butter. I lived in the U.S.A. for about a year and a half, and remember being surprised about it. The steak tastes different too! Our standard butter is 82.9% fat, just FYI!
I also thought about what was said about the weight of egg whites, so I weighed the egg whites I was using in a recipe tonight. They weighed approximately 39g each, almost 1.4oz. Thats almost 50% larger than you stated.... hmmm.... clearly we have giant eggs here, and I might need to start weighing mine too.
Looking forward to trying this tomorrow, Ill be chomping at the bit all day tomorrow waiting for tomorrow night so I can start!