The sleeping system is rad. It's nice to not roll off your pad. You can also join your two bags together, and not have to get a double wide pad, because the single pads stay in place.
Zipping bags together is quite nice and a lot warmer, especially when you sleeping in below freezing temps. So, I strongly recommend getting opposing zippers on your bags, so you can do this. Also, with Big Anges' sleeping system, your pads stay put, so you aren't rolling off them all night.
This isn't a super warm bag, thus the 4 stars. It's comfortable closer to 35+. But, I have discovered that the slightest covering over the top of the bag, will increase the warmth significantly. So, I recommend getting a sleeping bag liner and putting it over the bag and pad, to trap the heat. Or, taking a light blanket or even your backpacking towel, and draping it over the bag. This will increase the comfort rating dramatically.
Everything else I like about this bag. It's light and durable, even against my dogs claws. I just wish the temp rating wasn't 20 degrees off.
I do want to mention that it's crucial to fluff your down bag, before you use it for the first time. The down settles, and gets smashed while it's on the shelf, leaving dead spots that get cold. Put it in the dryer with tennis balls for a full cycle and you'll be set!