Thanks for that Serpenteer. I had some communication with John as well.
I have experienced the spikes first hand. That's why I have been testing with three different RPM sensors - Brushless Motor, magnetic and optical. The magnetic and optical provide very similar results. Not sure which one I was using in the graphs that are posted above. I definitely won't be using the Brushless Motor sensor though.
The advantage the Eagletree has over the Sentry is the sample rate. The Novak sample rate was 10 Hz (samples per second) and the eagle tree is 50 Hz. Thats 5 times faster. I want as many data points as I can get and the Eagletree should hopefully provide that.