Not a fan of the new UI - it's just not intuitive. Yes, bookmarks help and all but I still keep getting lost and / or have to navigate around far too many windows to get to where I want to go. Moreover, I just don't like the layout of various things such as the team selection page on match-day (the team sorting looks chaotic when you clear the squad), match results, transfer news for other clubs, etc
On the ME, definitely a much-needed upgrade but I am still not a fan of the 3D matches, it still doesn't feel remotely natural. I have switched back to the 2D Classic camera angle.
Bugs - I don't really have a problem with any of those as I assume the guys at SI will address them through future updates / fixes