Acutally, I was completely wrong above...I could only run that many instances becuase I had them sorted by things like Packet loss, Max ping time etc...and that ATE up CPU time.

Once I sorted by DNS name (that obviously does not change) the CPU utilization for the same set up as above dropped to 22%

Obviously, you can run a metric butt-ton (thats 2 craploads for the technicaly minded) of instances with NO issues...and a fat pipe.

Multi-ping ROCKS! (now please give it the rest of the functionality that Ping-Plotter has!)