It DEF relieves your bum
I've been using it about a week now and while it does relieve pain in the bum/back it's not like everyone says "like sitting on air"  BUT it does feel GOOD! Don't get me wrong. I've used it riding on the bus (plastic seats) and at my government building seat for 8+ hours and I have notices a sizeable difference, but around hour 6 if you haven't been moving around frequently you will still notice some fatigue in your lower back. They don't boast about eliminating back pain so I still gave them 4 stars.  It's also awkward to transport, but that's minor.
Rating: 4 stars