Cat photography with a typical consumer-level digital camera is a colossal pain. The problem is lag. Digitals are infamous for the variable delay between the time you first depress the shutter button and when the photo is actually taken. There's often a crucial second between the perfect expression and the photo, and a lot can happen in that period, especially with cats. In fact, that short time sometimes seems to stretch forever.
To give you a better sense of the problem, I made a little slide show of some of the many photos that missed their moving targets.
The slide show might take a minute or two to load, depending on the speed of your connection. Please excuse the wait.
If your browser can't play this little slide show, you'll need to download a free version of Apple's QuickTime player, available for both Mac and Windows operating systems.