The current app is pretty useful. I can
- access all the content that I have bought on dndbeyond
- view the player characters that are playing in my campaigns
- play my own character(s) as a player, including dice rolls if I want. For major changes to my character it redirects to the website, but it handles all common in-play updates directly in the app (hit points, conditions, inspiration, equipment, preparing spells etc)
Be aware that you can purchase new content in the app or on the website, and the prices may differ between the two. In my case, the app uses Euro prices including VAT, while the website uses USD prices where the Sales Tax/VAT will be added on checkout. Most promotions will only work on the website.
I can only say that in my experience, it works ok.