http://bugs.winehq.org/show_bug.cgi?id=23180
--- Comment #3 from Andreas Hermann Braml andreas@braml.org 2010-06-15 04:38:46 --- Is there a problem? Depends.
If you know about Alt-F4: no, there isn't. But if the X is all you know about closing windows (like my test user for the app; yes, I have "lab rats" for testing!) then there is. The app doesn't have a menu bar nor a button somewehre else to shut it down. And on Windows native the X is there and does what it should.
So if bug-for-bug compatibility is still a goal, this is a bug.
Else it's indeed 'minor', with an educative twist: the more people that know about Alt-F4, the better. I think that's why there's that T-shirt around ;)