Last week I ordered a refurb MacBook Air (Love it! btw). I ordered on Saturday afternoon. The order status shortly went from "Not yet shipped" to "Prepared to ship" - and then remained there for three days. It finally was shipped on Tuesday, even though the status page had said it would ship within 24 hours of ordering.
I spoke with an Apple Store rep on Monday, and he could give no information as to the delay. He started to offer to upgrade my shipping to Priority, but he could not edit the order to do so. It was kind of locked in and in limbo there for awhile.
Not really that big of a deal - it's just that, like the OP, I was anxious to get it asap 🙂