I buying my second serta deluxe this weekend. I'm replacing the one I bought in 2006, not because it wore out but because we got a bigger bed. The topper was never a thing of beauty, just a piece of foam and no cover. After 6 years it looks no better, but it is out of site under the sheets and it really made a difference with my back and knee issues. Since getting a new bed without the topper, my pains are starting to return and I get hand numbness when lying on my back.
Looks like most of the bad reviews are related to the odor. I remember the odor from the 2006 purchase. It went away after a while. I think the take home message is that some people are really sensitive to odors and some aren't. For me, the temporary odor was eclipsed by many comfortable years of sleep.