Topic: Cmd-W should close the tab, sh-cmd-w should close the window
The latest revision to the browser has changed the standard mac application behavior. A cmd-w now closes the entire window and all the tabs. Luckily it warns you first.
This is not how the old version behaved, and not how any other mac osx application behaves. cmd-w should close the current tab. You should be able to close the entire window and all of the tabs with shift-cmd-w.