There is a question that has not been addressed yet: how to handle numpy masked arrays. There are two modules, mostly compatible: numpy.ma and maskedarray. The latter will (I hope) become the standard implementation; until it does, we should have an easy mechanism for switching from one to the other so that we can test maskedarray. We also need to make it easy to routinely use the latter when it does become standard.
Maybe this needs to be added to numerix, and we need to use numerix internally via a single line per module:
import matplotlib.numerix.ma as ma
I haven't thought this through yet.