Saved me from buying a new mattress!
Love this topper.  It's so comfy and fits perfectly on the top of the mattress.  I took the advice of other reviewers and put my mattress protector over the top of it to hold it in place on the mattress.  However, the topper does compress during the night, so it benefits from being fluffed in the morning when making the bed.  So, I put a second fitted sheet over the topper, and placed it back on top of the mattress so I can keep it clean/protected but easily fluff it every morning.  It doesn't look as tidy, but the comfort is well worth it.