I think Apple innovates so often that if they add something that isn't innovative and is taking from other OS's people jump down their throats.
I'm not inclined to agree with this because just on this forum alone people complain that they wish Apple would implement features from Windows 7 even though Windows is several steps backwards, IMO.
Actually, Windows apps can run windowless. Most of them have icons in the systray if they do. It's really not that great of a way to do it as it's almost hacked on. I'm still not sure whether I like the indicators being gone yet. I'll have to wait till Lion is here and I can actually use it to determine how I feel.
I wasn't aware that Windows could run apps "windowless", I know you can minimize the window, I've never known that you could close the window and the app still runs. How is that possible?