Well... 2 weeks after I bought it, my car was in the shop getting an alignment because my tires were wearing very unevenly.
After that my wheel bearings needed to be replaced.
My check engine light came on and stayed on all winter long.
My "low tire pressure" light is constantly on.
My struts are very wore out and need to be replaced.
The whole time I had this car, in the winter the heater would not work even when I let it warm up for 15 minutes, and would then spend another 15 minutes driving to work. We have replaced the thermostat twice but cannot figure out the problem.
And now my current problems are I need a new fuel filter, which is conveniently located in the gas tank, and my ABS system is acting up and my brake pedal keeps grinding like I'm about to slide into something when I am on dry pavement. I'm scared I'm going to wreck!
I DO NOT like this car. I like the sporty look, but other than that it has been nothing but a problem that haunts me. I will never own another Pontiac, and I would recommend that others not own one either unless you like being constantly frustrated.
You bought the car with over 100,000 miles on it, you can't judge a manufacturer based on that.
Not only that, but many of those are simple fixes and can be expected with ANY car.
Replacing your thermostat isn't going to fix a no heat issue, the coolant doesn't flow through the thermostat on its way to the heater core. I would be looking at the control module, and heater core bypass valve first. Perhaps a little bit of diagnosis before you spend money on parts could help alleviate some of your frustration.
We have not had a problem with our 2005 Pontiac Grand Prix GT.
It was purchased new and has 50K miles on it now.
We are very happy with the car.