This issue is for Matplotlib version 1.5.1 and uses version 1.4.3 as a reference point.
Python version: Python 2.7.12 :: Anaconda custom (64-bit)
Platform: Linux (Springdale Linux, based on RedHat)
Installation method: Anaconda, for both Python and Matplotlib

Please note: I also have a StackOverflow question on this subject (where someone suggested I submit this as a bug report) which is useful as an additional reference for this bug: http://stackoverflow.com/questions/38985423/in-matplotlib-how-to-get-same-math-text-font-as-before-an-update

**In short, the issue is that the ring above the A when using \AA is higher in version 1.5.1 than it was in 1.4.3, and I think the 1.4.3 ring height is the correct one. The 1.4.3 ring height is the one I prefer at least.

After submitting the StackOverflow question, I downgraded my matplotlib back to 1.4.3 and verified that the ring height went back down to where it was before. It did.

Here is an sscce:

import matplotlib.pyplot as plt
plt.xlabel("$\AA \mathrm{\AA}$")
plt.show()

I've attached two images: the first image shows a detail of the plot generated above with version 1.4.3, focusing on the xlabel and the second image shows the same for version 1.5.1.