At first, I was surprised to see Apple in that list since they tend to do things their way. But it's true that they've used the iPod connector for ages and that it's been very nice to be able to use any iPod cables laying around to charge pretty much anything they've built since.
As Erik pointed out, it'd be nice to see something super easy to plug. I've never had much problems with the iPod connector, maybe due to the build quality. But USB (of all sizes, but regular USB in particular) has often times been a problem. It needs to either accept to be plugged upside-down or to be very simple to identify which side is up. USB is super frustrating on the latter.