Here are the details from the FAQ:
I just purchased a new smartphone during the holiday season, but if I knew that iPhone 4 was going to be available soon I would have waited. What are my options now?That's a narrow band, but Nov. 26 was in fact, Black Friday, so the start date make sense. Of course, $200 still leaves customers footing a large premium: full retail for Verizon’s iPhone 4 is $649.99 for the 16GB version and $749.99 for the 32GB version. A little math shows that those who purchased Verizon phones during the holidays will still be liable for a $250 premium fee on normal charge eligible upgraders and new buyers pay. In addition, you have to give up your current smartphone.
Current Verizon customers who purchased and activated new smartphones, feature phones or certified pre-owned phones between 11/26/2010, and 01/10/2011, are eligible to receive up to a $200 Visa debit card when they purchase an iPhone 4 at full retail price by 02/28/2011 and return their existing phone. Note: This offer is only available on consumer accounts with five lines or less, who are purchasing iPhone 4 through Verizon Wireless retail stores, telesales, or through verizonwireless.com.
Since the iPhone 5 is due out in the summer during the iPhone's annual refresh, we've already discussed that upgrading to a Verizon iPhone 4 may not be the best deal anyway. Of course, that doesn't help those who opted in during the above window, either.
In addition, you can probably do better on eBay with that brand-spanking new smartphone. Since the iPhone 5 is only a few months away, it might be better to hang onto your current smartphone and wait until then, then go the eBay route. You can probably get more than $200 there, even with additional 5 months of use (if you are gentle).
Oh, and those AT&T iPhone buyers who opted into the device recently despite the same above mentioned warnings? Sorry, there's not much help for you, and you might end up paying far more than a Verizon buyer because of the AT&T ETF fee.