Give the jagged nature of the graph, a more useful reading would be a moving average that smoothed out some of the up-and-down readings from the watch (I have a Garmin 405CX). Instead of taking each data point, take the average of the last 5-10. That could be plotted along side the individual readings as a checkbox selection on the graph.
I personally thing this would be more helpful to the average runner as the discrete data points don't appear to be entirely accurate although on average it is very accurate.
