I have had leased two Renault Meganes and with both of them I noticed a significant improvement in performance and fuel economy after a few months of driving. I live in the Jerusalem area and driving up the hills got much better after a while. I have no idea if it will be the same for Hyundai.
To poster #16, just because you don't pay for the gasoline when you have a leased car doesn't mean that it's not important to get good fuel economy. Someone is still paying for the gasoline and petroleum is a limited resource that is running out. Also, better fuel economy = less pollution.