My experience with the Cats Meow (purchased about 12 years ago) was that when new it was more like a 30 degree bag than its advertised 20 degrees. Of course by now (even though I have always stored it unstuffed and have used it only for car-camping the past 5 years) it's more like a 45 degree bag. Your mileage, of course, may vary. You may want to wear your insulating wear and a warm cap inside the bag on below-freezing nights.

Synthetics don't recover nearly as well from being compressed as does down. Try not to compress the bag any more than you absolutely have to to get it into your pack, and it will last longer. It's a good beginner bag. If you keep on backpacking, you'll probably want to save your pennies for a good down bag several years down the road.