On my previous 94 Grand Prix SE 3.1L at 165,000 miles, my head gasket blew and the head cracked in half. Other than that, just regular maintenance, (brake pads, Disc and exhaust.) The 94 ran for over 240,00 miles before I let my son have it, so he could trade it in for a 2004. It still ran like a top.
On my present 98 Grand Prix GTP, at 131,000, I am getting ready to replace my SC nose drive, instead of rebuilding it. The nylon type bushing was wearing, and I let it go too long, and now it is affecting my bearings. You can replace the bushing yourself, but to do the bearings, you need a Hydraulic press. I feel it is cheaper to go to ZZperformance.com and buy a completely rebuilt nose for $200 with better than OEM parts. If you plan to put a smaller pulley on, buy it from them and they'll install it for free when you buy the nose. Also, their bushing is of better material than that of the OEM one, and will last way longer.
As for the 98 Grand Prix GTP Coupe, I would not hesitate to buy another one. That car has surprised a lot of other newer and older muscle cars, including a newer Vette. From a dead stop at a light, he never got closer then my rear passenger window. He was winding it out for all that it was worth, and I never noticed I had it in 2nd all the time.
Being have been in the automotive building trade business for over 20 years, and dealing with the factories directly, there is no perfect model, brand or car. Each model, no matter how good it is, you are bound to get a batch that will have problems in certain areas. This goes back to the fault of quality control inspection, where the parts was made and/or assembled.