This is an update of my previous review.
Since my last review I've camped with this sleeping bag at below 32 degrees---there were ice crystals on my tent in the morning---and I was warm even without extra clothing, confirming that the temperature rating is accurate.
This bag has been redesigned for 2012. Specifically the neck opening is now quite a bit narrower. That's too bad, because the wide opening was a positive feature on the previous model.