* Mobile contact and calendar syncing: How well and reliably does it work?
* Calendar group features: how well do they work?
* Setup and maintenance: how much hassle is involved?
Sovereign doesn't solve all your operational problems.
I think it's suitable for personal use. I wouldn't run it in a production setting without thoroughly understanding all parts of the stack.
I would say it's good for personal use or to demonstrate what ansible is capable of.
* Mobile contact and calendar syncing: How well and reliably does it work?
* Calendar group features: how well do they work?
* Setup and maintenance: how much hassle is involved?