I've owned the 2005 Malibu for about 6 months and have 9000 miles on it. The ride is very smooth and comfortable. The engine is quiet and very powerful with great acceleration. I'm get 29MPG in overall driving with some highway and some stop and go traffic.
Sunroof, ergonomics, lumbar support, HUGE trunk, gas mileage, gas mileage, gas mileage...
The rubber bottoms for the cupholders are always coming out when I remove a cup or bottle. Many times I've walked into work with my coffee and the cup holder attached to it.