Has anyone tried shooting fast moving subjects (birds, cars, running animals) with Canon EOS 600D using Al servo autofocus? I am thinking of getting this DSLR but the internet reviews are a bit confusing on this point: that the 9 points AF (center cross-type) is not up to the task. What are the facts?
These two shots were taken with a 500D using the AI servo, which should be quite similar to the 600D. So it is certainly doable.
Bear in mind that these were shot with a good quality lens with ultrasonic motor. I could imagine that a lens that is fast to focus is at an advantage in these types of scenarios.
However, these two were the best two out of perhaps 200 shots. But that is mostly because I shot with a relatively slow shutter speed in order to get the impression of speed. This is just difficult and requires practice. Had I shot with a much faster shutter speed I am sure that a lot lot more would come out sharp (but not as interesting). But tracking the subject is also very difficult, particularly with only one focus point. The 7D has a much more advanced focusing system where you can select a cluster of focus points to use for tracking the subject, but I have not yet tried shooting this type of subject with the 7D.
To sum it up, if your main concern is shooting moving subjects, this might not be the right camera for you. The 7D would be a lot more suited, but of course it comes with a much higher price tag. Perhaps some of the other brands have cameras better suited for this task at a lower price, but I'm mostly just familiar with the Canon products.
If you on the other hand are going to shoot lot of different types of pictures, and occasionally are going to shoot moving subjects, then I think that this is a great entry level dSLR for you.
Yes, it will just get confused easier than a camera with a more advanced autofocus system. If the subject is moving in a relatively straight line with few obstructions you shouldn't have any problem. Add more complex movement and it may not keep up as well.
As another poster stated, the focus motor on the lens itself also plays a big part.
Usually, when one shoots a fast moving thing (race cars, or the bikes in @Pete's links) you pan the camera and try to have the subject be moving parallel to the camera. When the subject is coming straight at you, its much harder to get the focus right.
Proper panning takes practice, but can give wonderful results.
When it doubt, rent the camera/lens and try it yourself.