I just went to the Apple site, and went through the quick steps to get my $100 credit. If you need to get your credit, go here, and type in your cell phone number, and serial number. The serial number of your iPhone can be found inside the Settings > General > About section. Once you have entered these two items, you're sent an SMS message containing an code.

Simply enter this code, and your phone number into step two on the web site, and that's it. You are presented with a page that has your $100 credit. Just print it out for use in a brick-and-mortar store, or copy and paste the credit number and pin for use on the Apple Online Store.

I was going to get a new Nano, but opted for a iPhone dock that will connect to our home stereo (with remote!), a 2nd pair of earbuds with the little button on them for answering calls and advancing tracks, and lastly a $25 iTunes gift card. My total cost after the rebate was $3.