I've used several iOS devices heavily in the past two years and I'm not even certain what he's talking about. At no point have any of my devices become unusable

I've used several iOS devices heavily in the past two years and I'm not even certain what he's talking about. At no point have any of my devices become unusable due to notifications. If you can create a scenario where a dozen or more notifications pop up at once, and all vie for your attention, then you have my admiration, because that would be an awful bug. Unless you frequently schedule alarms to go off when your friends are going to be SMSing you and create twitter notifications, and you miss several calls at the same time, this is unlikely to be an issue. I suppose there is a small chance that Apple's push notification servers could bug out and delude your device with notifications, but everything I've read and seen about their architecture (from the perspective of a 3rd party app developer) indicates that this is designed to be impossible. Notifications (because they are disruptive) should not be able to render your device inoperable.