If the car has a FSH then I wouldn't worry about the reliability side. The biggest risk with hybrid car is the hybrid system but Lexus will extend the warranty on the high voltage battery until the vehicle is 15 years old - it will cost you around £60 per year.
Reliability aside, I think you will have to test drive it so you can feel the suspension. I had IS250 before my GS and was getting tired from the firm ride. I tested a GS with f-Sport and a with normal suspension - chose the normal one. The F-Sport GS still drives smoother than the IS though. On the other side, the IS was cornering much better.