For anyone who pre-ordered the Sprint version of the Samsung Galaxy S4 from Best Buy, you might want to check your email and/or talk to Best Buy. It looks like the supply chain delay has hit this version of the phone at Best Buy, as it will be delayed 2-3 weeks. Here's the statement from Best Buy,

We're sorry, but the fulfillment of your recent pre-order is taking longer than expected. We expect it to arrive between May 9 and May 20. To keep you informed of its delivery, we'll send tracking information once the item has shipped.

If you prefer, you can cancel this order at any time. To do so, please call us at 1-888-BEST BUY (1-888-237-8289). If possible, please have your order number handy.

If we don't hear from you before the order is shipped, we'll assume you still want this item and accept this delay.

Once again, we're sorry for this inconvenience, and we’ll do our best to make things right.
Just FYI, users have reported success in getting the phone directly from Sprint stores already. You may want to weigh the pros and cons of Best Buy's offer if you want to get the phone sooner.

Source: AndroidCentral