Since iOS 10, Apple changed how they handle push notifications, so currently that feature is not working on Apple devices. Since the last version of the app they also released a new programming language, so the new app will be built in Swift and from current tests it looks to load pages faster.
The app won't be ready for launch for (I suspect) another two months yet.
Meanwhile, the existing app has seen a few improvements as part of the overhaul. Posting via the app is much more reliable now and you can also post more than 4 pictures like with the website.
When the new app is launched I'll let everyone know. I hope, for most, it'll automatically push the update to peoples devices anyway.