Of course,it does depend on what route you take between Cappadocia and the coast and it will certainly take longer than 6 hours, but, not scenic!! there I would have to disagree. You can choose either northerly or southerly routes depending on your interests, but certainly worthwhile. There may also be the benefit of achieving a better rate for car hire with a longer rental period, try www.economycarrentals.com
for a good deal.
Down side of the car rental is the high cost of fuel so do go for a diesel, but if you enjoy the independance that a car gives you it is well worth doing.