I talked to 2 different reps yesterday (because you never know with those guys!) . . . And both confirmed that if you order the DX online through your Verizon Wireless account, they are applying the $100 on the spot - with no waiting for the Visa debit card.
BUT, if you pick it up in the store, you will have to do the rebate form, unless you can convince the store manager to give you an account credit.
They both also said that they're "anticpating" the online sales to start EARLY either on the night of the 13th or 14th, with free 2-day shipping. Of course, you may call and get a different answer. I'm just reporting what I was told.