Its a toss up between my 1979 Corvette and my 1985 Monte Carlo (the last GM product I will probably ever buy). The vette would die making a turn when it was cold. Almost caused a few real nice accidents. Was in the shop 1 week of every month I owned it and I owned it for 1 year. Cause of problem, finally? Stuck float in the front barrel of the carb. It took a call to the VP of sales in Detroit to get it fixed.
85 Monte Carlo - Dash caught fire two months after car was delivered (new). There was a short somewhere but they could never find it. Back to dealer too many times to mention. I finally got hold of the owner of the dealership, he sat in the car, smelled the burning plastic and turned to me and said, "if my techs can't see it they can't fix it, but I sure can smell it". I quickly traded it in on a Nissan.
No more GM for me. I drove imports until 2001 when I purchased my first PT Cruiser which I never had 1 bit of trouble with, nor the second one.

Pat