Challenging AI Servo Autofocus

I know there are lots of galloping horse pictures on the site, but there is a good reason for that. Because I can usually round up a rider and because galloping American quarter horses are very fast (called "World's Fastest Athlete" with some capable of over 50 mph), I have a consistently available and very challenging subject for testing camera and lens autofocus capabilities. Because I shoot this subject regularly, it is easier for me to differentiate the abilities of various DSLR cameras and lenses. Mix in some other scenarios and I can get a solid feel for a camera and lens' capabilities.