I've found that they love to lump together my impulse orders into one prime shipment. Got like a week's worth of impulse buys from this thread this evening. When they come together I suddenly realize that I've got a serious lack of time to tackle this pile!
It's been a pretty good service, especially with the combination with Amazon Lockers, which helps if you ever have issues with not being awake or around when packages arrive.
Thanks to youse guys I'm now a Vita owner. Sometimes working nights has its perks! I've found that one way to notice when a refresh has happened is to pay attention to the numbers of items in whatever category you're focusing on. Usually there's an uptick when the new things come in.