Bought my '07 in '09 as a certified GM used vehicle with 33k miles, upped the warranty to 75k.
At first, I was somewhat disinterested. Styling could stand to be less Cavalier-ey, but I needed something to get 25+ on the highway.
During my tenure of ownership (through 2012) it performed flawlessly. I put almost 43k miles on it in 3 years, and while it was never an 'awesome' car, it far, far exceeded my expectations. Wife traded it for an Avenger, and the car sold before we even got the new car off the lot.
I'll miss this one.
Upgraded Pioneer stereo. Driving lights (not fog lamps). My first impression of the transmission was lackluster, but over time as you get to know it, it starts showing you what it can do. Never had a problem getting up to speed to merge onto the interstate, and when passing was needed, she showed right up.
Seats needed to be a little bit less commuter-style and a bit more touring-style. They got rid of the Cobalt, so it doesn't make sense to make any new suggestions :)