The first symptom is that inline plots are about twice as large in Notebook 7 than they were in Notebook 6. This is very annoying itself.
It can be “fixed” by changing default dpi in .matplotlibrc from 100 to 72 dpi.
However, when I change the dpi to a higher number (for printing or when I need a crisper graph), the SIZE of the graph grows proportionally to the dpi setting. The correct behavior would be to leave the size unchanged, but of course increase dpi. So this is problematic.