I don't really see why there is so much concern for Power Nap. I don't see the practical benefit. Why do I care if email is downloaded while the MacBook is sleeping? The email will just download the instant I open the lid otherwise. Same for messages.
Why do we care if Time Machine makes backups while asleep? By definition, the computer is asleep, so no changes are made to the data!
I can see a mild benefit in having contacts, calendar, notes, etc update. This allows you to see the changes immediately upon opening rather than potentially seeing old data for a second or two. Still, is this worth the power usage and heat generation?