id say the first BIG problem ive faced is infact performance lol.
these cars arnt light, and lets face it, aftermarket is just over the mark of being non existant in comparison to other cars. its growing, slowly but surely.
Personally, ive been lucky with my LS so far. i think it ate the last owners wallet becuase ive drivin it for 10,000 miles since ive bought it and had zero problems besides normal maintence (fuel filter clogged). I pray it stays that way becuase i cannot afford it to try and eat my wallet too.
problems that ive noticed other people have...
window regulators
windows comming off track
Lug nuts
Clocksprings
Cooling system
Power steering (mine leaks)
Coils
Valve cover Gaskets
But on the upside i drive brand new toyota's everyday with under 100 miles to 8,000 miles on them, some of these cars even have problems. any car is going to have problems weather it be maintence or not. Its all apart of how you take care of it and how much its abused. working at a car dealership let me tell you people can absolutly DESTROY cars. Beat them horribly. People say theres ways to tell how a car was treated. these detailers have products that can make that very hard to tell wear on a car. some of its just luck of the draw. to be honest theres better options out there then the LS, everyone knows it. cars with cheaper parts, cars with less techno garbage to break.