I've just seen YET ANOTHER post relating to this problem, see http://arduino.cc/forum/index.php/topic,69742.0.html. That's the 4th post I've seen by a user experiencing this problem, and I only joined the forum about 2 weeks ago. Anything that's causing this much trouble for Arduino users needs to be addressed, preferably in the software, or failing that in the documentation.
- fix the bug that "delayMicroseconds(0)" delays for a very long time instead of a minimal time, so that "setAnalogReadDelay(0)" works properly.
I'm going to experiment with various analogue signal source resistances to see what delay is needed.