The seat has worked really well for us; our small dog feels comfortable in it, and we even managed the trip to Italy. Once he's inside, he calms down and sleeps. When it was hot, we added a cooling mat.
A dog that's a bit nervous about car rides feels more comfortable in this than just with a seatbelt on the seat. It's easy to attach to the backrest, and the flaps make it easier to handle the dog when needed. The car seats stay clean. One star off for the placement of the hole for the dog's seatbelt. It's at the back in the middle of the seat, so the dog's seatbelt doesn't sit very optimally.
I thought this carrier was very practical, but on our first trip, when my pet got stressed and agitated, he tore through the harness, which put us in danger in the car.