I placed an order yesterday afternoon, and the confirmation only came today. The odd part was that the message was time stamped yesterday, indicating that's when it was generated by the sales system...but it was delayed until much later.
This happened with my last order, too - it took over a day for the confirmation to arrive.
It's likely related to the mail server that sends these out being on several SMTP blacklists - http://mxtoolbox.com/SuperTool.aspx?action=blacklist%3a208.113.225.183.