Nice to know that Marmot has finally gone to the longer zipper! This allows for much better ventilation when it's warm.

I sold my Marmot Hydrogen a few years ago because it wasn't warm enough for me. I bought a Western Mountaineering Ultralight Super. The WM bag is cozy warm, and I really love that draft collar, but it sheds a lot more down than the Hydrogen did. I think the Pertex Quantum shell on the Hydrogen is superior to WM's shell fabric. As you pointed out, the zipper guard on WM bags is much better. Neither company has quite come up with the perfect bag, but WM is awfully close!