I submitted my scanned receipt and info on Monday afternoon and I'm still waiting for my download code from Apple. The 24 hours is obviously not from the time you submit your info but from the time Apple qualifies your order.
Mine took 5 days. Actually, I am glad it took this long since it gave me time to read then reviews on Lion. I have decided to wait a few months until Apple works out all of the Lion bugs. By the way, the Lion code does not have an expiration according to the email.