I've been patiently waiting for Mailbox on OS X to mature. Mailbox is my favorite iOS app (of all apps, not just email) and I want the same experience on my Mac. The Mac version has been in beta and often neglected, but I held out some hope it would become the full featured app I needed. When I heard the news that Mailbox was shutting down (iOS too), I was very disappointed, but assumed I could find a suitable replacement. Not much luck so far. I'm frustrated because a great app is going away and I don't think that's what needed to happen.
Mailbox on iOS or OS X never asked me for money. I was never presented ads or a subscription option. The point I'm trying to make that relates to iOS development is that I would have gladly paid for Mailbox. I would pay a yearly subscription or real money for the OS X app, etc. I want to give them money. Judging from others comments, I think there many would. So, fellow developers, there are business models that will work, if you provide a service customers want. There is a market to charge for good apps. You just have to find it and build a great app.
Saying Goodbye from Dropbox