I'm curious did you test and find that using non-persisted columns was faster than pre-calculating and storing all the permutations that you needed? (I guess it would probably depend on the storage system speed and a number of other variables.)
I find the aproach more manageable than using an SP and cleaner from the design point of view. And I can always make some other column persisted by a simple alter statement. (well not realy - has to be deterministic which is not the case with all columns). It is used primarily in warehouse solutions and therefore performance was never really an issue as it is loaded in an SSAS cube and persisted there. It also has a neat effect of being culture and language aware out of the box.
Hrvoje Piasevoli