I can find absolutely nothing wrong with this car. I love where the window buttons are to let the windows up and down. I like the size, the chairarms position and movability. Only thing I got a crack in the windshield in Jan. '08 and haven't gotten it fixed yet. My husband called at that time they were not even in stock for the new HHR's.
Color, design, I had white diamond pinstriping on it (looks like greased lightning haha smile), gas mileage. I did not get XM radio but we had it installed.
I get pretty good mileage and excellent driving power. I don't know how a 6 cylinder would be, (would that get rid of gas mileage?)