I bought the 09 model when it was on sale at Campsaver. Mine has the half zipper.
It doesn't appear to have that much loft, I think 4" is a bit of a stretch.
I had it with me this weekend for the first time. When I "went to bed" it was 35 F in my tent. I was wearing a t-shirt plus midweight baselayers, socks and head insulation. I was a bit cold at first, I guess I'm used to heavier bags "pressing" on me, the Phantom seemed to float above me. Once I fell asleep my body temp must have gone up, and I slept comfortably for about 8 hours when I decided to get out of the bag to check the temperature. It was exactly 32F in my tent at 5am. I was again chilly after loosing the heat trapped in the bag, and struggled for a while, seeking refuge near my wife's Ultralite. Again, as I fell asleep I warmed up.
I'd say the temperature rating is accurate. But it depends a lot on the person using it. I'm 5.10 and 140 lb, not built to conserve heat.