This mattress has been amazing so far. It expanded almost immediately to its full size. It didn't smell weird and we were able to sleep on it that night. It is extremely soft, cradles my hips and shoulders perfectly and has almost no bounce. I'm a side & tummy sleeper and this bed has been amazing for my shoulders so far. With my old mattress, my arm would go numb throughout the night and I would have shoulder pain all day. Since using this mattress (going on 3 weeks) all of that has stopped. 
As far as sleeping hot, it's hard to tell since it's winter right now and I like my room freezing cold. Time will tell how the mattress performs during the hot summer months, but as of now, I do not have any complaints.