We don’t have the DataTypes we had before like AppendableData and StructuredData. Now we have MutableData and ImmutableData only.
safe-js is a third party library and @joshuef can explain better about this one.
As far the browser DOM apis are concerned, the approach will be the same. APIs will be injected to the safe: pages. But definitely the APIs will change for the same reason I just mentioned. As you would be knowing, we had to change the DataTypes to allow apps to scale easily.
We understand how the design actually turns out when we start using it, the various scenarios come across and also from the varied inputs from the community. We do regret for breaking changes and in the early stages it becomes unavoidable at times. These changes definitely fill the gaps we identified from previous releases. safe_app module will be much easier to use and understand, when it is ready and tested.
2017 should be a smooth sail 