I just bought a L Certified 2018 GS FSport with 20K miles and I am amazed at how quiet and rattle free this car is. Super solid, even in Sport+ mode which really stiffens the suspension.

 

I'm at 16,000 miles now. Around ~6,000 I had a nasty sunroof rattle. Took it to the dealership & they took care of it and it's been solid since.

Around 15,000 miles, mine developed a very buzzy and constant rattle coming from near the cupholder & transmission shifter area. It was annoying to live with. Took it in just last week to get this resolved and the dealership was awesome. According to them, they heard it right away on the test drive so they removed the center console, re-tightened every bolt, added "insulation" (which I'm assuming is some sort of felt tape) and then put everything back together. It feels solid now and the rattle is gone. It also stopped all the creaking noises it would make when passengers would rest their legs on the side of it.

Other than those two things, for the crappy roads we have here, it's been a pretty solid and rattle-free car, though my Infiniti Q50S was probably the most rattle-free car I've ever had. It never developed a single rattle and it had run-flat tires and a very stiff suspension (way harsher than GS F-Sport even in Sport S+ mode).

 

I had this issue with my 2015. I took console apart and added some felt tape, not a single rattle since. It's a common area for rattle in our GS. Lots of plastic parts in that area that tends to causes rattles. They should add more insulation felt tape in that area at the factory.