Very comfortable.  Not as much support as I would like for walking, but perfect for a slipper.  I can wear them on short errands (like a starbucks run) and they are warm and not obviously a slipper in appearance, but feel soft like one.  They are also warm.
They run a little small, I had to return the first pair and got a full size larger which fits perfectly.
They are by far the best slippers I have ever had and well worth the money.