He seems to sleep well on it and it's comfortable to lay on. Has held its shape for the 18 months we've had it. 

I'm not sure if this is a mattress issue or a bed issue (I purchased both from Wayfair) but the twin mattress is considerably smaller than the twin bed frame, and we have to be careful that my young son's legs and feet don't get caught between the mattress and frame when he's getting in and out of bed. We've pushed the mattress forward so the gap is next to the wall, but it's a sizeable gap.