I've found that their notification system is too slow. There must be some kind of delay between when an item is shown to be "in stock" and when the notification emails are sent out. For example, on Monday of this week I checked for small pistol primers... In stock! Yeah! So, I purchased small pistol primers. Then, the next day, I get an email stating that an item I'm interested is in stock. Yep, small pistol primers that I already purchased the day before and they are long gone by the time the notification email is sent.
All that said I still like Midway and purchase most things from them.