I researched online and spoke with Optima owners. Kia has come a long way in reliability in the past few years. I was surprised by the level of owner loyalty. People who own Optimas enthusiastically recommend them.
I test drove all comparable mid-size cars. Of the group, the Ford Fusion, I thought, had the best balance of responsiveness and ride. The Kia has more initial lean in corners (European style), but otherwise is as fun to drive as the Fusion.
Engine is remarkably quiet for a four (except under strong throttle use). Cabin wind noise is well muted. Road noise was initially bothersome, but has decreased with tire wear.