I have a customer upgraded from UCCX 10.6 to 12.0 recently. Upgrade worked well.
The agent work with both Finesse (no surprise) and Jabber as softphone. Calls are fine but there is a display that is no okay for agent : the finesse popover is at the same screen location that is Jabber (at the bottom right). I put a screenshot in attachment showing the behaviour.
My idea was to move the popover a little upper through Finesse Admin layout configuration but I didn't find a way to do that.