It's nice that Ping Plotter gives you the average ping, but what I'd be really interested in is seeing standard deviation.

I pretty much keep a constant ping going to my first hop (my ISP) because my service is so lousy (5% packet loss for the last 866,000 packets). And often the latency is all over the place (current high on the 60 minute graph is 80 while the average is 13). So for me seeing the standard deviation would be helpful.