I like that annotations let me place arrows whose shape stay the same when I resize the axes, yet the positions of the arrows move with the axes.

However, I would like to be able to specify a different line attributes for the arrow head and the connector (arrow line). Specifically, I want to have a zero line width for the arrow head and a non-zero line width for the connector. Perhaps the user could specify things like the line width, line style, and line color in the connectorstyle string. For example:

anno = ax.annotate('', xy=target, xycoords='axes fraction', \
         xytext=orig, textcoords='offset points', \
         arrowprops=dict(arrowstyle='-|>', mutation_scale = 200, \
         linewidth = 0, connectionstyle = 'arc3, linewidth=1'))