mhodgson wrote:though I tend not to use continuous shutter even on fast moving aircraft.
Same here. In fact, the 50D has two continuous shutter modes - high speed is ~6 frames a second, and low speed is ~3 frames a second; my camera is always on low speed.
But even then, very rarely do I use it. Even with the camera on AF Servo, I'll still usually release and re-press the shutter button completely for each shot. Not sure why - it's probably a hold over from my old Rebel XS, which could only shoot 1.5 frames/second and had a tiny 3- or 4-frame buffer.
For very low shutter speed shooting, I might take 10-20 shots of a particular aircraft, spaced over 10 seconds.