We bought a Tempur mattress and loved it during winter months, but summer was unbearable, far too hot!
We eventually gave it away to a charity shop (it was still as good as new) and bought a hand made mattress with 2500 pocketed springs. It's very firm and has a summer side with cotton just under the cover and a winter side with cashmere, so it's warm or cool to sleep on. We do have to get DS to help DH turn it though, it's very heavy!
The only 'problem' if it can be called that is that the mattress is very deep, 11", and getting fitted sheets of that depth can be a bit difficult.