I set the matplotlibrc tick.direction to out.
The ticks on the top x-axis and left y-axis appear to begin on the inside edge of the frame and thus appear shorter than the other two sides which seem to begin on the outside edge of the plot frame.
The minor ticks are almost obscured.
I am using the default settings for all else in the matplotlibrc.
Running matplotlib 0.84, OS X 10.3.9
This in/out choice is a new feature and perhaps this is a bug.