I purchased Royal Frosting from a local nursery last year, so I have seen it through two bloom seasons and I have been impressed with it both seasons.
It is a beautiful white with a creamy overlay and diamond dusting--such a pretty shimmering in the sun. Last year it was a whiter white than this year and I'm not sure why... It could be due to location (it was moved to a spot that gets more shade this year). It was also a little heavier on the substance last year--likely due to fertilizers the nursery uses--but was still a flower with nice substance this year, too. Despite being moved to a less-sunny, poorer soil area, it still thrived.
One of its best features is it's high bud and branch count, regardless of whether or not it is fertilized. Another favorite feature is its sweet scent. Hybridizers will also appreciate it's easy pod (and pollen) fertility... I got lots of seeds off of this plant both years.
When I think of what a traditional-form, white daylily should be, this is what I think of.