For the last 20+ years I have the same solid wood bed frame with (common in central Europe) slatted frames (aka "duckboards") under the mattress. No boxspring.

I sleep like a baby for the last many years. I think that is due to a lot of things that have nothing to do with either the frame or the lack of a boxspring. No alcohol, good nutrition, lots of exercise (including passionate sex!), a regular sleeping schedule when I'm not traveling, no finanial worries, meditation, and a healthy and happy relationship with my wife.