How does the new UMG work?

Please give me an overview of what can be done or cannot be done with UMG within unreal engine?

I haven’t yet run into any issues with using UMG, being able to bind tasks to blueprints make’s it as flexible as Blueprint scripting.

Mathew Wadstein has a ton of useful Tutorials on the subject

You can do everything that is possible on Scaleform + much more with integrating via blueprints. Basically it’s a full UI solution. There are even plugins to construct it dynamically with ease, have the styling done with HTML/CSS and much more.