1) Hero portrait information when you click on enemy / ally heroes
Why do you need a pop up window which blocks the screen instead of the old replacing your own hero information with theirs when you click on another hero. You can instantly focus on the information you want like hp/mp or skills because it is at the exact same position as your own hero portrait before it switches to the other hero portrait. And now since it pops up as an overlay, your first instinct is to press escape to close it instead of F1 to switch back to your hero portrait and information.
2) Kill Information
After a decade of having the kill information display on the left side above the mini map, suddenly it is switched to the right side for no reason at all. It is so confusing for old players to adjust to and I miss a lot of the kills when they happen. Then I suddenly look over to the top bar and realize the monkey king in my team is dead. This is probably one of the most frustrating changes to the new HUD. It is like changing the cars in your country from left hand drive to right hand drive or vice-versa. I mean come on what is the reasoning behind that change.