After buying it used from the dealership, for the first four years we enjoyed the car. But I have always disliked the electronic throttle system (GM should have stayed with the regular wire). At first I didn't mind it, because the transmission was always smooth. But needless to say, it causes so much downshifting, as it always wants to be at a low RPM.
So eventually my transmission started slipping at 156,000kms... I maintained this car from the inside out, and I did not expect this, since owning a 94 and 98 Grand Prix's prior to this 04. I am not sure what caused the transmission failure, but I've never had transmission problems this early in a GP. So I drove the car until I couldn't take any more of the hard shifting, and eventually got my mechanic to change the transmission. This was the biggest downfall of the car. The rebuilt transmission is okay. It's not as smooth as it once was before.
To add, the engine burns oil. Furthermore, it seems like I am changing the sway bar links constantly...
In the summer, I get "Charging system failure" when it's really hot out when idling; maybe the alternator is going out, who knows. Everything checks out okay after many tests.
Back seats are uncomfortable. They are flat. The previous Grand Prix's seats were much better. But I like the option that they fold down on this model.
The car has never left me stranded. The only major repair was the transmission. Other than that, the car is reliable.
In my opinion I feel the previous generation 97-02 GP'S were better built cars. Minus the cheap looking plastic material used in the interiors.
Overall, the car handles good and has nice styling. I like the dashboard and the set-up. Yes, the information display screen doesn't have the same options as the previous GP, but it does the job.
I still own the car. It is a black fully loaded Grand Prix. Leather, sunroof etc. Looks great for a 9 year old car. Fuel economy isn't great, but is decent for a V6. I am still wanting to test drive the supercharged Comp G model.