I have 17k on my 2006 G6 GT. No major issues, but the alignment seems get changed easily, slight vibration at highway speeds, slight brake vibration (might be warped - sudden brake to avoid deer), sometimes the speakers sound weird, Continental tires don't hold pressure well (one flat, one bulge), cheap components and paint (already fading), some suspension noises during the winter months, steering make some ticking noises during parking lot manuvers. Most of these I've read on other posts, so I don't see much improvement between 05 and 06.
2006 Pontiac G6 GT (3.5L V6)
2003 Chevrolet Impala LS (3.8L V6)
2002 Chevrolet Camaro Z28 (5.7L V8)