I'm in the middle of evaluating my gear. I have another bag for those cool fall nights but I'm in the need for a sub-zero bag.
I've used this bag on one trip (this past winter) inside a cabin. There are no rips or tears, the zipper works flawlessly.
Rated at 20deg but I believe you can push that a few degrees colder with proper sleeping apparel.
$120 shipped to your door (lower 48) +$8 for AK or HI. I can do money order, check or paypal (will hold shipment for check to clear).