I got the seat for my firstborn who is quite picky if it comes to strollers and carseats. He tried it out as soon as we unboxed it and settled in right away!
To begin with, it is slightly smaller and narrower than the main seat, but can still fit my 2 yo comfortably and looks like will be comfortable for him for at least a year more.
Liner is nicely padded, buckles are great (magnetic). I can really recommend it to all growing families, as it will allow to keep a carrycot with newborn in the upper position.