I'd also add that when it comes to shipping code to a client, pointing them to a Python download vs. shelling out for a MATLAB license can be a factor as well. I like MATLAB but there's no denying there's a degree of sticker shock with it.
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That echoes my experience. I generally prefer Chaco for plots in Python since it seems to handle large datasets better than matplotlib (although matplotlib seems more functional), but matplotlib is comfortable for MATLAB users. I'm working on a SciPy project with a couple of MATLAB refugees and they love matplotlib.