Mailbox has been one of the go to apps for iPhone users as an alternate to Gmail app, and until recently it had a reservation system. Mailbox was bought out by Dropbox and soon the app was available free of cost for iPhone without any reservation. However, the app remained an iPhone exclusive for a while, but finally the iPad version of the app is out now sporting the same simplicity and clean UI as found on the iPhone app.
Like mentioned, you do not have to wait anymore to get your Mailbox application, and you can simply go to the app store and directly download it. The app is very similar to how Gmail app is on iPad, sporting a two pane layout, where the left pane shows the Mail list while the right pane shows the contents of the mail that has been selected. The larger size of the iPad means that reading mails is a breeze. The gestures on mailbox on iPad are exactly the same as that on iPhone, so if you have used the app on iPhone, there is literally zero learning curve. You swipe right to archive the mail and swipe to the left to set it as a reminder.
The only downside of the app so far is the fact that it only supports Gmail accounts as of now, we do hope though that there would be an option to add more mail accounts other than Gmail in the near future though. You can download the app for free here.