So far we have been pleased with the fuel economy. It is not as good as a Civic but far better than our previous Ford Taurus with the V6 Vulcan engine (this car has replaced the Taurus).
We have only owned the Ion for a few months so I cannot comment on the reliablilty yet.
The control design is good but I would change a few things like the location of the rear defrost and recycled air switches. The cup holders are too close to the dash board as well IMO. Other than that its average.