What a job. We ended up purchasing a compound miter saw. Much, much easier and nicer.
Anyway, we heard the 28" to 36" rule, too. However, once we started we simply held up a piece and stood back and decided where it looked best. It ended up being 36" from the floor (however, we measured 35" from the quarter molding because we have carpet in some rooms and wood floors in others.
That is something else you need to consider. If you are using the molding in more than one room on the same floor, make sure you like the height you pick in each of the rooms because they will need to be the same.