The frameon argument shifts the plot axes to the right leaving a strip of blank canvas to the left of the plot axes, while increasing the figure's width. Altogether, a highly undesirable side-effect.

pylab.plot(range(10));
ax=pylab.gca();
ax.legend('test', frameon=False)

I'm using 1.2.0rc3

A search for frameon in issues produced nothing describing this problem. A wider google search uncovered a couple of references to this problem but the solution still eludes me.