Opinions vary... I consider 30mpg @ 70mph in a car this size to be pretty bad based on past experience. Had I come from a Full sized Dodge pickup getting 16mpg on a good day I'd have to say 30mpg would sound pretty darn good. My 05 & 08 Corollas both delivered a consistent 38-40mpg in the same driving conditions that the Aveo delivers around 32-34mpg in. The Corolla was a bigger smoother car and required nothing but tires and oil changes but I hate the way the new 09+ Corollas drive, thus the Aveo in my driveway now.
For what I paid for the car brand new, I can't complain. For the difference between the price of a nice used 08 Corolla and the price of a new Aveo, I can buy a lot of gas....and if I drive slow enough, the Aveo can beat the best MPG I got with the Corolla. If in 3 years, my experience has been similar to yours, I will be an extremely happy Aveo owner and will likely stick with a GM brand. My first year with the Aveo has been pretty good; hopefully it will continue.