The Verge have posted a review of the app, claiming it has, "just fixed email on the iPhone." - http://www.theverge.com/2013/2/7/3961544/mailbox-app-for-iph...

It will be interesting to see whether it lives up to the hype, but everything I've seen so far points in that direction.

However, despite registering within ~10 minutes of the reservation announcement, there are apparently 16,222 people in front of me in the queue.