We bought this queen-size mattress to replace 2 twin mattresses, so we're having a little problem with sharing a bed again (we had a king-size bed and had to switch to twin four years ago). But the mattress itself is wonderful, very comfortable. We don't feel any movement when the other person moves around. The edge is quite firm, so there's no feeling that we will roll off if we get too close. It is not too firm and not too soft--just right. The only thing is that one of us feels a little hotter lying on it, but that could be due to summer heat. The other person does not feel hotter. 
We did lots of research before buying this mattress and feel that we made the right decision in choosing it. We would recommend it to anyone looking for a new mattress.