This lets you respond to email at your own pace. For me, working through my email once in the morning and once after lunch seems to be a good pace. My coworkers quickly adapted, and will use an instant message or phone call if something really needs immediate attention.
This might not be as easy for non-programmers, but for me it helps me get more done since I can focus easier, which is ultimately what will keep my boss happy. In more tricky environments, you may be able to configure filters so that important emails do send notifications.
Hopefully in the future we can all have a digital assistant that watches our email for us and detects the level of urgency automatically.