Not "puffy pants" but I use snow pants.
They have them that are insulated and waterproof/breathable AND with cargo pockets so they actually almost look like regular pants. I got them a touch big so I can wear them over regular pants but I can wear them by themselves just fine also - maybe with silk pajamas underneath or polarfleece pants.
I got these 686 brand in coyote brown when they had them last year at REI:
http://686.com/products/men/outerwear/pants/l6w210-686-mens-authentic-infinity-cargo-pant/oliveThe bottoms have snaps to fit over ski boots so they are kind bell bottomed. I sewed on another set of snaps so that they are NOT bell-bottomed bit I have the option to use them with ski boots
I think these are better than the KUIU, for example, because they're less expensive and are kinda better in contact with wet snow because the synthetic insulation will come back more easily from compression and the waterproof material will at least try to prove its claim. They are heavier though.
