Yep...I am actually using mine today as a layer under my down jacket. Surprisingly warm, very durable, perfect for a fall rock climbing jacket, and a very versatile piece given the air it traps between layers
I have been climbing with the Marmot Windshirt for years and I think it's the perfect jacket. Packs in its own pocket and clips on your harness while you're leading a pitch, unpacks in a jiffy - the super light two-layer aspect is awesome. It's got some windblocking ability and also a warm, soft inner layer.