I like the app as it helps me to focus on the real work to happen. Simple and straight forward. Get me my mails in doses. It's a good help on a way to more discipline.
Have been using this for about a month and love that I don't get distracted by constant flow of emails throughout the day. All emails are attached to a label if you really want to "peek" before the scheduled delivery time(s) you've set-up.
If you value your time and work you need big, focused time intervals to focus and creative thinking. Connection to the network should be restricted to 1 hour 1-3 times per day max for email, phone calls, and whatever social crap you are stuck into.
How is this product different from the competitors? Is there any possibility to delete spam?
If Google doesn't add this, I'd be worried about a developer making an add-on. it is a time-based rule that diverts e-mails to folder and then dumps them back to the inbox at certain times.