There is a significant jump in firmness from the Midnight to the Twilight; however, it is just a great mattress. I would recommend it for anyone with chronic low back pain. 

I have bulging discs at L4-S1with radiculopathy in my right lower extremity. I have slept on TemperPedic, Thermagel, SLeep Number, and King's Down; nothing has held a candle to Helix.