I have committed a new set of colorbar code, mainly in its own file (colorbar.py), and renamed the originals to pylab.colorbar_classic and figure.colorbar_classic. All examples using colorbars that I could test have been modified if necessary, so that they work with the new version.
For a quick introduction, try contour_demo, contourf_demo, and image_masked.
The kwargs for the new version are quite different from the old, so this will cause breakage. There are several possible ways of dealing with this, including using rc to simply specify which version of the colorbar is used. I would prefer to avoid adding compatibility stuff directly to the new colorbar.
I think that the new colorbar has enough advantages over the old one to justify complete replacement as a goal.