One example: You can't close other tabs directly once they've shrunk - you need to bring up a menu on the tab. If you do click on the left side of the tab (where the x would be), it'll expand and now your cursor is ... somewhere. Maybe over the x! Maybe over an extension icon! Maybe over another tab! Never mind, move the cursor to the x and oh no, you've missed it by a pixel and now you've activated the address box which also disables the x. Which means you now have to click somewhere else outside the address box and navigate back to the x for closing.

(On a system where you have the infinite Fitts width of the menu bar, it seems perversely insane to have these tiny shifting boxes that mess you around.)