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Doesn't appear to be that many people who have exchanged / reported back on it.

Word from various forum posts is that they'll give you a USB adapter that came with your device.
If you've an iPad 3 they'll give you a 10W charger. Not the 12W that's on the shop floor. It'll come in non-retail packaging for you.

The luckier (and rarer ones) report that they got the 12W charger.

If I had to hedge, you won't get an upgrade of your charger, just another one similar to the one that came with yours in a non-retail packaging.

Process takes 45 minutes because it's ultimately a genius appointment (after you've spoken to an employee who knows how the exchange program works).
 
Purely for historical information

Exchange was completed on Friday, 18 October 2013
Some stores made exception but the below was a good rule of thumb.

1. Required a Genius Bar Appointment to exchange the device as it qualified as a "repair event"

2. Adapter that is exchanged is based purely on the device that you had brought in.
If you brought in a iPad 3, you'll get a 10W adapter back. There's no free upgrade to 12W adapter. You would get another 12W if you brought in an iPad 4 instead.

3. No testing of the fake adapter done. I had brought in Apple like chargers and they were happy to replace without any questions asked.

4. Only adapters were given. Items were retrieved from the store's inventory in brown envelops / boxes. No retail packaging involved. No USB cable etc. Your old adapters are collected and packaged up again.

5. Whole process takes about 30 minutes. Most time is spent on the administration of processing your request in their systems.

Program is now officially over. Hardly a loss for Apple in my opinion.
 
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