Confirmed in 14w31a.
@[Mod] CubeTheThird
I just tested it, it's kind of fixed but not really. When you turn on fullscreen and alt-tab, now it just turns fullscreen off, you still have to go back in options and turn it back on, I just don't have to press the fullscreen button twice now, just once.
I believe this is fixed in 1.8-pre3.
Awesome.