Look at the plug itself. You will see something along the lines of (these are the numbers off my Veer's plug):
Input: 100-240V~ 50/60Hz 0.2A
Output: 5V= 1.0A
What this says is the plug will work on almost every power system in the world. But the plug itself only pulls UP TO 0.2 amps. So the input would be somewhere between 20W and 48W, though I'm betting closer to 20W. The output is in DC voltage and is set at 5W.
Why only 5W when the input is 20W? Unfortunately, converting from VAC to VDC is not a very efficient process especially when dealing with two different voltage levels.
Watts = Volts * Amps. So as the voltage goes down, so does the available power (watts). Despite a five fold increase in Amps, the voltage drops over 95%.
So a 10W plug at 5VDC will have a current of 2A. These are the numbers you need to look at. If the output voltage on the iPad differs than that on the TouchPad, DO NOT USE IT! If the iPad output Amps is LOWER than that of the TouchPad, it just won't work.
I'll be getting my TouchPad in a couple days. When I do, I'll look at the numbers and get back on here (assuming no one else jumps in first).