Love ours and when we upgraded to a king sized bed, my husband wouldn't even consider purchasing another type of bed. We never did well with traditional box spring, and this really does help my back out a lot. Especially knowing that I can adjust it.
Don't skimp though, I don't find the lower models to be as comfy as the upper ones.
There isn't a bed out there that I sleep better on though, and I've slept on some really awesome ones in my life. Box springs just put too much pressure on some points for me... can't take them long term w/o significant pain.