I was wrong.
To illustrate this for you I have put together a simple little "game" that has arrow buttons and a little "character" that those buttons move around the screen. I use the terms VERY loosely. At any rate, if you run the following code on your iPad/iPhone/iPod Touch you will be able to see what I'm talking about.
To play around with this you will need to put this html file on a web server. If you don't have access to a real one you can set up a local one on you wifi network using WAMP.
Once you get it up and running it should look something like this -
As you can see. It takes a bit from the time you touch the buttons until the time it actually moves the hero. I did a lot of digging (so you don't have to) and found out that there is ANOTHER iOS specific event called ontouchstart.
Replace all the ontouch events with ontouchstart and fire up the "game" again. See the difference? Instant gratification.