It's not that it will close a window with a bunch of tabs without asking if maybe I didn't want to close them ALL even though it feels the need to tell me every fucking time I go full screen that I've gone full screen when basically the only reason that I ever go full screen is to take a screen shot which I can't do until the stupid notification goes the fuck away.
It's that it will close a window with a bunch of tabs for no reason. Not me hitting a button, not something freezing up (I know this because it does ask me if I want to kill things that have become unresponsive) nothing at all. Just one moment the window is there, then it's gone. I can reopen it, and all tabs in it, but using the command to reopen the most recently closed tab but in all likelihood whatever important thing I was doing in said tabs will have been lost.
When I hit the wrong X and lose things because of that I can accept that. I fucked up, I pay the consequences. When I do nothing of the sort and lose things for no legitimate reason and without so much as an error message that pisses me off. More than somewhat.