Rear suspension clunk noise due to faulty stabilizer bar links, fixed under warranty.
Blower motor developed a squeak, fixed under warranty.
Air bag light came on due to a bad module, fixed under warranty.
There were a couple of recalls that were taken care of as well.
I looked at many used vehicles before deciding to limit my search to a GM product, mainly due to the fact that GM products have always held up well for me, and are relatively inexpensive to maintain. I was not impressed with the Malibu's design, so I looked at the Impala, and was pleasantly surprised by the ride and handling. It was comparable to a Buick Lacrosse I looked at (which shared the same platform until this year). Very comfortable, and a good, solid ride.
The 3.5 V6 and 4T45E transaxle are proven components that are easy to repair/maintain.
Although I will admit city MPG could be better (average 18-20MPG), this car really delivers outstanding highway MPG for this size of a car (29.8 MPG).
The car has a lot of nice standard features, although since mine is a former rental, it does not have Onstar or Satellite radio, but that is not an issue for me. The radio in this vehicle has a CD player and auxiliary input, and is very good for a stock radio.
One comment if buying used... look for a dealer that sells GM Certified Used Vehicles. Not all GM dealers participate in this program, but mine does. In addition to the basic 3 year/36,000 mile bumper to bumper warranty, GM Certified adds an additional 12 months/12,000 miles to the warranty. Powertrain warranty is 5 years/100,000 miles. If you can find one of these that is under a year old, inspect it thoroughly, verify the history (I will not buy a car that has been registered in states that use heavy road salt in the winter) and if it passes the inspection, these cars are really a good value used, especially with the additional warranty.
As far as service, my dealer has been very good at addressing my concerns. However, I perform routine maintenance myself.