UnitedHealthcare, the nation's largest insurer, does not get top marks from consumers for its core product: Health insurance. 

According to the American Consumer Satisfaction Index, five of UnitedHealthcare's major rivals –– Humana, Kaiser Permanente, Blue Cross Blue Shield, Anthem and Aetna –– were ranked higher by their customers, although United's score of 66 was only a tad lower than Humana and Kaiser's top score of 71. The only company that truly came out looking bad was Cigna, which came in last place with a score of 60. Perhaps the silver lining for Cigna is its pending merger with top-performing Anthem.  

But according to a new report from J.D. Power, a market research firm, UnitedHealthcare's vision and dental plans have the most satisfied customers.