Wow! I haven't had much time to hang out on WC this past week...
I guess more people are open to using black in oils than watercolor and pastel.
I myself am going to be using a limited Zorn palette for an oil portrait workshop and had to get over my "no pure black" bias! (although I know Zorn painted with a few additional colors, this seems to have been used in a lot of his portraitures)
I do think that black in pastel and especially watercolor can overwhelm a painting and make spots look "dead. In both pastel and watercolor I find it more effective to mix my own blacks. In oils though, it seems that there are some excellent paintings that use black effectively.
I am enjoying seeing how ivory black mixes with various colors- amazed it makes a muted violet with cadmium red light... The grays I am getting are really pretty.
Here is my little chart made with yellow ochre, cadmium red light, titanium white and ivory black. All M. Graham paints on Arches oil paper.