So-So
I bought this cushion for my daughter for her birthday.  We make several 13 hr. trips in the car every summer and fall and she was having real problems with comfort while driving.  We just made one of the trips, so I asked her how she would rate it.  She gave it a firm 3 stars.  She said it was definitely better than the seats in the car, but she was still plagued with "butt fatigue" through the trip.  Ironically, while we were there, she bought me a seat cushion for $20 that I would give a 4-5 star rating.  I should have saved my money!
Rating: 3 stars