You need to be able to tell that a window is private. That's the only thing (and it is a major thing) that stands in the way of me making it my default browser. It's too easy to confuse a non-private window and then get tracked and cookied to death. It is a hassle to remove all that junk.
Indeed, I would like the option to ALWAYS open every window as a private window!
Password function fight with 1Password and make it extremely difficult to click on the right password popup.
Ron