I'm mostly interested in the tactics and watching the match engine in practice. I've found it pretty easy to adapt to the new UI so far, although it is alarmingly buggy and unfinished.

Tactics are the most relevant for me. The different offense-defense tactics looks very good and I think it's much more realistic and more like real football. I also hope they haved reduced the annoying and repetitive tasks of long-term saves (e.g. talking to players and journalists that often), as I am usually going for saves longer than ten seasons. Time to take my home club into CL Final :D