I like the 0 degree bag, although it is rather bulky, I take it on colder hunts when weight isn't so much a concern. I don't trust that temp rating on the thinner bag...I would probably be pretty cold if I were out in that thing at 30 degrees. And the bivy is just way to heavy/bulky for my use. My 7oz TiGoat does everything I need it to for about 1/2lb and minimal space.
About the only Army/military gear I take hunting are the waffle mid-weight layers, silk weight layers, and the big puffy primaloft jackets that you seem to only get if you're stationed in Alaska, Korea or Drum.