Continuous Servo Focus on a Nikon

I've come across various different names for this, follow through focussing, or in Nikon's case, they call it Continious Servo Focus.
Basically, I mean the additional autofocus setting that some cameras have to allow them to keep focus on a moving object.
Has anyone had much experience of doing motorsport photography with this function setting on the camera?
I haven't used it at all for any motorsport photography, but I did experiment a bit with this setting for the cycling events at the Commonwealth Games, both for straight on shots and panning shots.
So, I've not really used this function much at all (just for a couple of the cycling events) and wondered how other people had got on with it.
I was shooting at either 500th/sec shutter speed and aperture of F16 or F22 with a 28-300 zoom with 400asa film. I was quite surprised by the very narrow depth of field. Any suggestions if I was doing anything wrong? Or of how this works best?

Apologies for the quality of the scan, here's an example of the sort of photos I was coming up with.

my d100 panics using that setting on the 50-500 and goes way out of focus. in fact i find the autofocus on that lens with that camera so poor i use manual at all times now.

So far I've found the AF on the 50-500 to be absolutely fine. Usually at the track with the Pentax I've used autofocus to get the general focus on an area and then fine tweaked with manual from there.
I'm not entirely convinced that the continuous focussing would work with track photos, but I might give it a try at some point during the season.

just make sure it's on a clio test day or something unimportant ;). i assume because you switch between continuous and manual focussing the switch on your camera's easier to use than mine...