Oh and if you are selling it to a "look before they purchase" buyer, you may want to take a slightly different approach. I would want to see the iPad working before I handed over cash for one, to check version number of s/w and memory at the very least. Once you do a complete wipe you'll be at the "connect to iTunes" logo screen and this will negate the ability to check things out before they hand over the cash.
So instead just use the iPad settings feature to erase all content and settings AFTER they inspect the item first.
This is common for Craigslist transactions....not so much for eBay.