My baby has disliked this bassinet since day one.
I understand the mattress has to be firm to be safe, but you can hardly call the one that comes with this sleeper a "mattress"; it feels like cardboard. I think it may be unlevel, too, because my baby always rolls right up against the side with the zip-down wall.
I put this bassinet on my registry so I could put it up against my mattress and, sadly, it's too short.

Also, it says in the description that it has " breathable" mesh walls, which it does, but there's a thicker cushioned strip that goes along the bottom of the zipper side, and my baby always gets her face pressed directly up against it.

Overall, it's been difficult to get my baby to sleep well in this bassinet, and I expected more for the price.