Questions on Colgate foam mattresses

I've read everyone's comments and reviews and am curious 1. Who is it that has rated it number 1 (I am assuming the Fields?). 2. Doesn't the foam become less soft more quickly than coils and thus pose a greater hazard? I would think that the foam would more easily be "smooshed" down from weight of baby, especially as he/she gets older. 3. Is the foam *really* firm? I am so worried about having a mattress firm enough and I was shocked in BRU yesterday how soft some of them were. 4. Does anyone have more information on the study suggesting SIDS when passing down mattress from child to child?

Thanks for any and all help-
Debbie