The Serta Malloy Firm mattress was firm throughout the entire mattress.  I did not "fall" in when I sat at the edge of the bed.  It is very firm and I was originally worried that it would be too ridged to even sleep on but after the first few days and now weeks of use I noticed that no matter the position, I am comfortable and it gives just enough and provides excellent support to my hip and back as a side sleeper.

Movement was isolated to the area that it occured in, meaning that when my husband rolled over or adjusted his sleep position during the night I could not feel it on my side of the bed.  The Sleep True boxspring provided enough support to the mattress and I have yet to notice any noise or creaks when getting in or out of the bed.  Sleep quality has not improved over the past few weeks but it has also not worsened.