Having just tried saving to .pdf with MPL for the first time in years (potentially in place of .png, for embedding in .tex files), it looks great, except for an obvious glitch. I'm using FreeSans as my default font in rcParams, 13 pt size, and when saving to .pdf, the '0' character comes out distorted. Same goes for 'B' and '8', but none others that I can tell. This doesn't happen when saving to .png. Here's the example code

plot(np.arange(10))
text(0, 5, 'abcdefghijklmnopqrstuvwxyz\nABCDEFGHIJKLMNOPQRSTUVWXYZ\n012345687890\n~!@#$%^&*()_+-=')
gcf().savefig('freesans_example.png')
gcf().savefig('freesans_example.pdf')

You'll have to set FreeSans as your default in rcParams to replicate this, or pass it the appropriate way when plotting or adding the text. I'll see if I can attach the output.

I suppose since this doesn't happen in the .png, this must be a PDF backend bug, and not some quirk in FreeSans?

Martin