I use a silk liner, but not for warmth or to keep the bag clean. I just find it more comfortable, especially in warmer weather when I tend to sleep in less clothing. End result is I don't end up sticking to the nylon of the sleeping bag. And in really hot weather, I push the sleeping bag off to the side and use the liner alone as a sheet, which is just warm enough. So, for me, it's well worth the weight.