I have had my Cube for nearly a year. Highway mileage is around 32 mpg and city is around 26. It handles well for a small car. I've made one long trip of 2300 miles and everything went fine. I'm a big guy and the room inside this car is amazing for it's size.
Pretty much everything is good. I especially like the headroom.
I would like a little more storage inside the car; perhaps a drawer under one of the front seats. There is a weird reflection at night so I think the angle of the windows could be changed a little.