Maybe 2 Hours after it was available to pre-order. Got my email from Sprint. You have to check your order status with order number starting with oy because the one that starts with DM does not show anything.
My new Galaxy S4 will be here before 4:30pm! Unfortunately one of the cases that I ordered won't be here until after May 10 and the other one that I purchased is now getting terrible reviews from people who JUST got their Galaxy S4's (I assume from AT&T), so I will certainly not be using that one. That's the risk you take when you order something online that hasn't been released to anyone yet. Oh well.
CHECK SPAM Folder for Sprint email, Thats where mine was for Gmail.
Woke up early today and first thing I did was check my emails. Saw a bunch from the forum but none from Sprint. So I checked the order status and saw it was shipped. Then went back to my emails and saw the Sprint one in my spam folder sent last night at 12:23am. My S4 will be here today by 4:30!!! YEAAAA