Wow, I ordered mine on May 13th and it's showing the same ship/delivery dates as you. I hope my order status changes soon. I'm getting jealous with all these iMacs out for delivery today.
Right after I posted that, my phone buzzed: "A transaction with Apple Online Store has been made." WooHoo!!!
I work a night shift, something tells me my productivity level will be decreased over the next few nights while I refresh my order status over and over and over again.