I had a Cobalt LS for 18 days as a rental car in Alaska in August/September 2007. Overall, I thought the car was pretty good. The one I had was an LS four-door sedan. I'm guessing that this one was a pretty basic model since it had no power windows or door locks. This is a pretty small car, but I thought that the inside was adequately comfortable. I never sat in the backseat, so I can't comment on the comfort of the backseat. The drivers side seat was comfortable and the seating position was good. The upholstery on the seats was not the best looking cloth, but not too ugly. I was amazed at the room in the trunk. Tons of room, and really deep.
I never bothered to calculate the mpg I got with the car, but I think it was quite good. Even with the automatic transmission, the car had good acceleration. I was satisfied with the amount of power it had. The handling and steering seemed a little vague and sloppy, but was not too bad overall.
The things that I noticed right away that I didn't like was the unpleasant finish on the dashboard and doors. The dashboard and the plastic on the doors was made of rock-hard plastic with a very rough, sandpaper-like texture. Now, I know that people don't spend a lot of time touching dashboards, but this one not only felt awful, but it looked cheap and nasty. Having that nasty, rough plastic on the doors is uncomfortable when your arm comes into contact with it. The steering wheel was made out of cheap plastic (?) that was very hard with very little "give". The handle molded into the drivers door had a kind of sharp "edge" that really dug into my thigh when I had my left foot up by the seat while I drove.
Overall, I thought the car was not a bad mode of transportation. The impression I got was of a decent car that seemed a little unrefined on the interior. Based purely on what I experienced, if I were in the market for a new car, I would consider getting a Cobalt, provided it had a nicer interior.