Sorry for the late reply on this topic but I promis I am in the trenches on this exact issue.
Currently my ST class app(android) is working and I use it daily. I hope they don't break it because the new system is not even ready for developers yet
I have been working on learning the new platform but a week ago they upgraded the system and released a new API a week ago and were supposed to release a new Android/IOS app to work with it. They have not released the app yet so I have not been able to write code for a week now
Until the app is released my test code does not work.
As for features. I use my custom AD2 screen every day. I use it to arm/disarm etc. From what I can tell we will be able to have some level of control of a screen still. It is not 100% clear yet but it is not a new topic of discussion with other developers.
The big improvement is that it will no longer require any code or github etc to get working. SmartThings/SamSung has approved my brand AlarmDecoder and it will show up on your SamSung TV, ST App etc as a known device.
Best
Sean Mathews