Well, I just bit the bullet and cancelled my pre-order, after pre-ordering in-store at Best Buy. Unfortunately, I'm not one of the lucky ones that got the phone right away. The salesperson said he wasn't sure when my pre-order would be fulfilled & that there were other pre-orders before mine, but he did say "probably after June 2nd."
Cancelling the wirefly order at this point is still a gamble, but it makes a little more sense for me. I only got $50 off on Wirefly, not the $80 that a lot got, and Best Buy's $50 gift card deal is still going, so I don't lose any money on the switch. Plus I wasn't going to be able to be home whenever it shipped, so it'd probably add another day to shipping, and then they would have to leave it at my house, which is a little risky where I live.